# Free Compass Math Practice Questions on Substituting Values Into Algebraic Expressions with Solutions and Explanations - Sample 11

 Solutions with detailed explanations to compass math test practice questions in sample 11. What is the value of 2(x3 - y2) + 2(x3 + y2) for x = 2 and y = -4? Solution Substitute x and y by their values and simplify 2(23 - (-4)2) + 2(23 + (-4)2) = 2(8 - 16) + 2(8 + 16) = -16 + 48 = 32 If x = 3, what is the value of 6 / x + 4x - 20? Solution Substitute x by its value and simplify 6 / x + 4x - 20 = 6/3 + 4(3) - 20 = 2 + 12 - 20 = -6 The surface area A of a cylindrical container is given by the formula A = 2 pi r2 + 2 pi r h where r is the radius, h is the height of the container and h its height and pi is a constant which can be approximeted by 3.14. Which of the values below is closeset to the area of a container whose radius is 10 cm and its height 5 cm? A) 628 B) 1256 C) 314 D) 3140 E) 942 Solution Substitute r, h and pi by their values in the formula for the area. A = 2(3.14)(10)2 + 2(3.14)(10)(5) = 628 + 314 = 942 If x = - 2 and y = 3, what is the value of - x- y? Solution Substitute x and y by their values and simplify - x- y = - (-2)(-3) = - 1 / (-2)3 = - 1 / -8 = 1 / 8 If y = -3, what is the value of (y3 - 3) / (- y + 3)? Solution Substitute y by its values and simplify (y3 - 3) / (- y + 3) = ((-3)3 - 3) / (- (-3) + 3) simplify = (-27 - 3) / (3 + 3) = -30 / 6 = - 5 What is the value of 3 x3 - 2 x2 + 2 for x = - 2? Solution Substitute x by its values in the given expression 3 x3 - 2 x2 + 2 = 3 (-2)3 - 2 (-2)2 + 2 Simplify = 3(-8) - 2(4) + 2 = -24 -8 + 2 = -30 If x = 2.7, what is the value of x + 0.75(x - 1.5) + 1.2? Solution Substitute x by its values in the given expression and simplify x + 0.75(x - 1.5) + 1.2 = 2.7 + 0.75(2.7 - 1.5) + 1.2 = 4.8 If x = - 0.07 and y = 1.2, what is the value of x y - 0.2 (y - x)? A) 0.338 B) - 0.338 C) 0.3 D) - 0.3 E) 0.338 At normal resting heart rates, the mean arterial pressure MAP can be approximated by the simple formula MAP = DP + (1/3)( SP - DP ) where DP is the diastolic pressure and SP systolic pressure. Find the mean arterial pressure MAP, rounded to the nearest unit, for a person with systolic pressure SP of 101 mmHg and a diastolic pressure DP of 72 mmHg. A) 85 B) 100 C) 90 D) 80 E) 82 What is the value of 3 / (x - 4 y) + 2 / (0.5 x + 8 y) for x = - 2 and y = - 0.25? A) 11 / 3 B) 3 / 11 C) - 3 / 11 D) - 11/3 E) 3