Tsk math review

The table above shows the high temperature last ursday for ve cities, A through E. If the median of the ursday high temperatures for these cities was 81°F, which of the following could NOT have been the high temperature last ursday for City A ? A. 85°F B. 75°F C. 65°F D. 55°F

Choice (A) is correct. If the median of the ursday high temperatures for the ve cities was 81°F, then when the ve high temperatures are listed in order from greatest to least (or least to greatest), 81°F must be the third temperature in the list. Since the three greatest known high temperatures are 93°F, 87°F and 81°F, the unknown high temperature for City A must be less than or equal to 81°F. Of the given choices, only 85°F is NOT less than or equal to 81°F, and therefore only 85°F could NOT have been the high temperature last ursday for City A.

There are 20 children in the cast of a class play, and 8 of the children are boys. Of the boys, 4 have a speaking part in the play, and of the girls, 8 do not have a speaking part in the play. If a child from the cast of the play is chosen at random, what is the probability that the child has a speaking part? A. 52 B. 12 C. 53 D. 34

Choice (A) is correct. Of the 20 children, 8 are boys and so 20 − 8 = 12 are girls. Of the boys, 4 have a speaking part in the play, and of the girls, 8 do not have a speaking part in the play, so 12 − 8 = 4 girls do have a speaking part. erefore, 4 + 4 = 8 of the children have a speaking part. It follows that if a child from the cast of the play is chosen at random, the probability that the child has a speaking part is 8/20 = 2/5

In the xy -plane, what is the y -intercept of the graph of the equation y = 2(x+ 3)(x− 4)? A. −24 B. −12 C. −2 D. 12

Choice (A) is correct. e y -intercept of the graph of an equation is the y -coordinate of the point in the xy -plane where the graph intersects the y -axis. us the y -intercept can be found by setting x = 0 and solving the equation y = 2(x+ 3)(x− 4) for y. erefore, y = 2(+0 3)−(0 −4=) 24 is the y -intercept of the graph of y = 2(x+ 3)(x− 4).

x4 −1= A. (x+1)(x−1)(x2 +1) B. (x+1)2(x−1)2 C. (x+1)3(x−1)1 D. (x−1)4

Choice (A) is correct. e y -intercept of the graph of an equation is the y -coordinate of the point in the xy -plane where the graph intersects the y -axis. us the y -intercept can be found by setting x = 0 and solving the equation y = 2(x+ 3)(x− 4) for y. erefore, y = 2(+0 3)−(0 −4=) 24 is the y -intercept of the graph of y = 2(x+ 3)(x− 4).

Which of the following equations has both 1 and −3 as solutions? A. x2 −2x−3=0 B. x2 +2x−3=0 C. x2 −4x+3=0 D. x2+4x+3=0

Choice (B) is correct. A quadratic equation that has both 1 and −3 as solutions is (x −1)(x + 3) = 0. Multiplying this equation out gives the equation x2 + 2x − 3 = 0.

The variables x and y are directly proportional, and y = 2 when x = 3. What is the value of y when x = 9 ? A. 4 B. 6 C. 8 D. 12

Choice (B) is correct. Since the variables x and y are directly proportional, they are related by an equation y = kx, where k is a constant. It is given that y = 2 when x = 3, and so 2 = k(3), which gives k = 2 . erefore, y = 2 x, and so when x = 9, the value of y is y = 2 (9) 6.

If 5−x=4,thenx= A. −21 B. −11 C. 1 D. 11

Choice (B) is correct. Squaring both sides of the equation 5 − x = 4 gives 5 − x = 16 , and so x = −11. Substituting −11 for x in the original equation, one can see that −11 is a solution of the equation. erefore, the value of x is −11.

If3t−7=5t,then6t= A. 21 B. −7 C. −21 D. −42

Choice (C) is correct. If 3t − 7 = 5t , then 5t − 3t −= 7 , and 2t = −7. erefore, 6t = (3)(2t=) −(3)(−=7) 21.

The yard behind the Cindy's house is rectangular in shape and has a perimeter of 72 feet. If the length of the yard is 18 feet longer than the width w of the yard, what is the area of the yard, in square feet? A. 36 B. 144 C. 243 D. 486

Choice (C) is correct. If the length of the yard is 18 feet longer than the width w of the yard, then w = 1−8, and so the perimeter P, which is P = 2( w)+, can be rewritten as 2(+−18) = 2(2 18−). Since the perimeter of the yard is 72 feet, it follows that 2−18 = 36, and so = 27 and w = 27 −18 =9. erefore, the area of the yard is (27)(9) = 243 square feet.

If x−1=20, then x= x A. −21 B. −19 C. −1 /19 D. 1 /21

Choice (C) is correct. If x −1 = 20, then x −1 = 20x. It follows that −1 = 19x, or x = − 1 /19

A ball was kicked into the air from a balcony 20 feet above the ground, and the ball's height above the ground, in feet, t seconds a er the ball wasw kicked was 2 h(t) = 20− 16t+ 32t. What was the maximum height, in feet, of the ball above the ground a er it was kicked? A. 32 B. 34 C. 36 D. 40

Choice (C) is correct. e equation h(t) = 20− 16t+ 32t is equivalent to h(t) = 2−0 16t(−t 2). It follows that h(t) = 20 when t = 0 and t = 2. us the maximum value of this quadratic function occurs when t is halfway between t = 0 and t = 2, which is when t = 2 − 0 1. = erefore, the maximum height, in feet, of the ball above the ground a er it was kicked was h(1) = 2−0 16(1+)2 32(1=) 36.

(3x2y3)3= A. 3x5 y6 B. 9x6 y9 C. 27x5y6 D. 27x6y9

Choice (D) is correct. By de nition, (3x2 y3 )3 is equivalent to (3x2 y3 )(3x2 y3 )(3x2 y3 ). By the commutative law of multiplication, this expression is equivalent to (3)(3)(3)(x2x2x2)(y3y3y3). Since (3)(3)(3)=27, x2x2x2 =(x⋅x)⋅(x⋅x)⋅(x⋅x) =x6 and y3 y3 y3 = (y ⋅y ⋅y) ⋅(y ⋅y ⋅y) ⋅(y ⋅y ⋅y) = y9 , it follows that (3x2 y3 )3 = 27x6 y9.

A group of 18 people ordered soup and sandwiches for lunch. Each person in the group had either one soup or one sandwich. e sandwiches cost $7.75 each and the soups cost $4.50 each. If the total cost of all 18 lunches was $113.50, how many sandwiches were ordered? A. 7 B. 8 C. 9 D. 10

Choice (D) is correct. Let n be the number of sandwiches ordered. en 18 − n was the number of soups ordered. Since the sandwiches cost $7.75 each, the soups cost $4.50 each and the total cost of all 18 lunches was $113.50, the equation 113.5 = 7.75n+ 4.5(18− n) holds. Multiplying out this equation gives 113.5 = 7.75n 81+ 4.−5n, which simpli es to 32.5 = 3.25n, or n = 32.5 10. = erefore, 10 sandwiches were ordered.

There are 3x − 2 trees planted in each row of a rectangular parcel of land. If there are a total of 24x −16 trees planted in the parcel, how many rows of trees are there in the parcel? A. 21x−18 B. 21x−14 C. 8x D. 8

Choice (D) is correct. Since there are 3x − 2 trees planted in each row of the parcel, and a total of 24x −16 trees planted in the parcel, it follows that the number of rows in the parcel is 24x −16 , 3x−2 which can be rewritten as 8(3x−2)=8.

In the xy -plane above, point C has coordinates (6, 9). Which of the following is an equation of the line that contains points O and C ? A. y=x 3− B. y=x 3+ C. y=23x D. y=3x 2

Choice (D) is correct. e coordinates of point O are (0, 0), and the coordinates of point C are (6, 9). It follows that the slope of the line that contains these two points is 9 − 0 = 3 . 6−0 2 e y -intercept of any line through point O is 0. erefore, an equation of the line that contains points O and C is y = 3 x. 2