Arithmetic Reasoning

From 1980 through 1990, the population of country X increased by 100%. From 1990 to 2000, the population increased by 50%. What was the combined increase for the period 1980-2000?

Be careful with combined percent increase. You cannot just add the two percents, because they're percrents of different bases. In this instance, the 100% increase is based on the 1980 population, but the 50% increase is based on the larger 1990 population. if you just added 100% and 50% to get 150%, you would of chosen the wrong answer. The best way to do a problem like this one is to pick a number for the original whole and just see what happens. The best number to pick here is 100. If the 1980 population was 100, 100% increase would put the 1990 population at 200. A 50 % increase over 200 would be 200 + 100 = 300. Since the population went from 100 to 300, that's a percent increase of 200%. 300-100/100 x 100% = 200/100 x 100% = 200%

If a car travels 1/100 of a kilometer each second, how many kilometers does it travel in an hour?

Find the number of seconds in a hour and then multiply this by this by the distance the car is traveling each second. There are 60 seconds in a minute and 60 minutes in 1 hour. in 1 second the car travels 1/100 kilometers in 1 hour the car will travel 3,600 x 1/100 or 36 kilometers.

On a map, 3/4 inch represents one mile. what distance, in miles is represented by 1 3/4 inches?

In this question, the ratio is implied : for every 3/4 inch of map there is 1 real mile, so the ratio of inches to the miles will represent 3/4 to 1. Therefore, you can set up the proportion. Number of inches/ Number of miles = 3|4/1=3/4 add across (4+3=7) then move your 1 to make it a mixed fraction. Now 1 3/4 inches = 7/4 inches. Set up a proportion: 7/4 Inches / Number of miles = 3/4 Cross Multiply: 7/4(4)=3(Number of miles) The 4's cancel one another out. 7=3(number of miles) 7/3=Number of miles or 2 1/3 = Number of miles. Answer is 2 1/3.

Ms. Smith drove a total of 700 miles on a business trip. If her car averaged 35 miles per gallon of gasoline and gasoline cost $1.25 per gallon, what was the cost in dollars of the gasoline for the trip?

Ms. Smith's car averages 35 miles per gallon, she can go 35 miles on 1 gallon. To go 700 miles she will need 700/35, or 20 gallons of gasoline. The price of gasoline was $1.25 per gallon so she spent 20 x $1.25, or $25, for her tip.

20-(-5)=

Subtracting a negative number is the same as addition, so 20-(-5) is really 20+5=25.

If 50% of x is 150, what is 75% of x?

The calculations aren't too bad on this one. The most important thing to keep in mind is that you're solving for 75% of x and not for x itself. First, you are told 50% of x is 150. That means that half of x is 150, and that x is 300. So 75% of x = 0.75 x 300 = 225. The answer is 225.

4! =

The exclamation mark indicates a factorial. A factorial is an integer multiplied by every smaller integer, down to the number 1, like this: 4! = 4 x 3 x 2 x 1 = 24.

A student finishes the first half of an exam in 2/3 the time it takes him to finish the second half. If the entire exam takes him an hour, how many minutes does he spend on the first half of the exam?

The time it takes to complete the entire exam is the sum of the time spent on the first half of the exam and the time spent on the second half. The time spent on the first half is 2/3 of the time spent on the second half. If "S" represents the time spent on the second half, then the total time spent is 2/3S + S or 5/3S. You know this total time is one hour, or 60 minutes. Set up a simple equation and solve for S. 5/3S = 60 3/5 x 5/3S = 3/5 x 60 S = 36 So the 2nd half takes 36 minutes. The first half takes 2/3 of this, or 24 minutes. You could also find the first half by subtracting 36 minutes from total time of 60 minutes.

Four people shared a taxi to the airport. The fare was $36.00, and they gave the driver a tip equal to 25% of the fare. If they equally shared the cost of the fare and tip, how much did each person pay?

The total cost of the taxi ride equals $36 + (25% of $36), or $36 + (0.25 x $36) = $36 + $9 = $45. If four people split the cost equally, then each person paid $45/4 or $11.25 each.

The total fare for two adults, and three children on an excursion boat is $14. If each child's fare is one half of each adult's fare, what is the adults fare?

This is a question where Back solving (plugging in an answer choice to see if it's correct) can save you a lot of time. Let's start with choice B and see if it works. If B is correct, an adult's ticket would cost $3.00, and a child's ticket would cost $1.50. The total fare you're asked for is for two adults and three children. If an adult's fare was $3.00, that total fare would be 2($3.00) + 3($1.50) = $6.00+$4.50= $10.50. That's too low since the question states that the total fare is $1400. Now see what happens if an adult fare was more expensive. If D was correct, an adult's ticket would cost $4.00 and a child's ticket would cost $2.00. The total fare would equal 2($4.00) + 3($2.00) = $8.00 + $6.00 = $14.00. That's the total fare you're looking for. so D is Correct.

What is the prime factorization of 140?

To find the prime factorization of a number, find one prime that will go into the number (here 2 is a good place to start). Express the number as that prime multiplied by some other number. 140 = 2 x 70 Then keep breaking down the larger factor until you are left with only prime numbers. 140 = 2 x 2 x 35 140 = 2 x 2 x 5 x 7 The answer is; 2 x 2 x 5 x 7.

A painter charges $12 an hour while his son charges $6 an hour. If the father and son worked the same amount of time together on a job, how many hours did each of them work if their combined charge for their labor was $108?

When the painter and his son work together, they charge the sum of their hourly rates, $12 + $6, or $18 per hour. Their bill equals the product of this combined rate and the number of hours they worked. Therefore $108 must equal $18 per hour times the number of hours they worked. Divide $108 by $18 per hour to find the number of hours. The answer is 6

A certain box contains baseballs and golf balls. If the ratio of baseballs to golf balls is 2:3 and there are 30 baseballs in the box, how many golf balls are in the box?

You can express the ratio of baseballs to golf balls as 2/3. Since you know the number of baseballs, you can set up a proportion: 2/3 = 30/x where x is the number of golf balls. To solve, cross multiply: 2x = 3 x 30. to get 2x = 90, 90/2 = x = 45. Answer is 45.

A subway car passes 3 stations every 10 minutes. At this rate, how many stations will it pass in one hour ?

First, set up the rate as a proportion, here x is the number of stations. 3 Stations/ 10 Minutes = x Stations/1 hour. Then, convert the units. 3 Stations/10 minutes = x stations/ 60 minutes Cross Multiply and solve for x. 3 x 60 = 180/10x Simplify. 180/10x = 18x Answer is x=18

John Bought a camera on sale that normally costs $160. If the price was reduced 20% during the sale, what was the sale price of the camera?

This question asks you to determine the sale price of a camera that normally sells at $160 and is discounted 20%. To solve, determine what 20% of $160 is. Take the percent made into a decimal; 0.20 x $160 = 32. Take that $32 dollars and subtract it from $160. $160 - $32 =$128. Answer Is $128

Marty has exactly 5 blue pens, 6 black pens, and 4 red pens in his backpack. If he pulls out one pen at random from his backpack, what is the probability that the pen is either red or black?

To find probability, determine the number of the desired outcomes and divide that by the number of possible outcomes. The probability formula looks like this: Probability = # of desired outcomes/ # of possible outcomes In this case, Marty is pulling one pen at random from his knapsack, and you want to determine the probability that the pen is either red or black. There are 5 blue pens, 6 black pens, and 4 red pens in the knapsack. Let's return to the probability formula: Probability= # of desired outcomes/ # of possible outcomes # of red + black pens/ # of red + Black + Blue pens = 4+6/ 4+6+5= 10/15=2/3 the answer is 2 out of 3 times you'll pull a red or black pen, or 2/3.

If a man earns $200 for his first 40 hours of work in a week and then is paid one-and-one-half (1 1/2) times his regular rate for any additional hours, how many hours must he work to make $230 in a week?

To learn the man's overtime rate of pay, first figure out his regular rate of pay. Divide the amount of money made, $200, by the time it took to make it, 40 hours. $200 ÷ 40 hours = $5 per hour. That is the normal rate. The man is paid 1 1/2 times his regular rate during overtime, so when working more than 40 hours he makes 3/2 x 5 per hour = $7.50 per hour. Now figure out how long it takes the man to make $230. It takes him 40 hours to make the first $200. the last $30 are made at the overtime rate. Since it takes the man one hour to make 7.50 at this rate, you can figure out the number of extra hours by dividing $30 by $7.50 per hour. $30÷$7.50 per hour = 4 hours. The total time needed is 44 hours.

After eating 25% of the jelly beans, Brett had 72 left. How many jelly beans did Brett have originally?

You are given the percent decrease (25%) and the new number (72) and you're asked to reconstruct the original number. Don't just take 25% of 72 and add it on. That 25% is base not on the new number, 72, but on the original number - the number you're looking for. The best way to do a problem like this is to set up a equation: (original Number) - (25% of original number) = New number x-0.25x= 72 0.75x = 72 x = 96 Alternatively ,you can use the answer choices to determine the correct answer. The original number of jelly beans has to be reducible by 25%, or 1/4. that means the original number of jelly beans has to be a multiple of 4 (or else you'd be reducing by pieces of jelly beans.) Only the correct answer, 96, is a multiple of 4.

A 25 ounce solution is 20% alcohol. If 50 ounces of water are added to it, what percent of the new solution is alcohol?

You're asked what percent of the new solution is alcohol, The "part" is the number of ounces of alcohol; the "whole" is the total number of ounces of the new solution. There were 25 ounces originally. Then 50 ounces were added, so there are 75 ounces of the new solution. How many ounces are alcohol? 20% is 1/5, so 1/5 of 25, or 5 ounces are alcohol. Now you can find the percent of alcohol in the new solution: % Alcohol = Alcohol/ Total solution x 100% = 5/75 x 100%= 20/3% = 6 2/3%