iB l 43. Physics I h e force you n e e d to apply to a lever varies directly w ith th e w eight
you w an t to lift. Suppose you can lift a 50-lb w eight by applying 20 lb of force to a
certain lever.
a. W hat is th e ratio of force to w eight for th e lever?
b. W rite a n equ atio n relating force a n d weight. W hat is th e force you n e e d to lift a
friend w ho weighs 130 lb?Challenge The ordered pairs in each exercise are for the same direct variation. Find each
missing value.- (3,4) an d (9, y) 45. (l,y)and(|; — 9 ] 46. ( - 5 , 3) an d (x, - 4 .8 )
- Gas Mileage A car gets 32 m i p e r gallon. The n u m b e r of gallons g of gas u sed varies
directly with th e n u m b e r of miles m traveled.
a. Suppose th e price of gas is $3.85 p e r gallon. Write a function giving the cost c
for g gallons of gas. Is this a direct variation? Explain your reasoning.
b. Write a direct variation equ atio n relating th e cost of gas to th e m iles traveled.
c. How m u ch will it cost to buy gas for a 240-mi trip?
St a n d a r d i ze d Test Pr ep GRIb D ED RESPON SE
^AT/ACT 48. The price p you pay varies directly w ith th e n u m b e r of pencils you buy. Suppose
you buy 3 pencils for $.51. How m u ch is each pencil, in dollars?- A scooter can travel 72 m i p e r gallon of gasoline a n d holds 2.3 gal. The
function d{x) = 72x represents th e distance d{x), in miles, that the scooter
can travel with x gallons of gasoline. How m any m iles can th e scooter go with
a full tan k of gas? - The table at the right shows th e n u m b e r of h ours a clerk works p er w eek and
th e am o u n t of m oney she earns before taxes. If she w orked 34 h p e r week, how
m u ch m oney w ould she earn, in dollars? - W hat is the greatest value in th e range of y = x 2 — 3 for the domain
{-3, 0, l}?
Weekly WagesIB
12 9 9 .0 0
17 1 4 0 .2 5
21 173.25
32 264.00
VI WmMixed Review
Find the slope of the line that passes through each pair of points.- (2,4), (0, 2) 53. (5, 8), ( - 5 , 8) 54. (0, 0), (3,18)
Get Read y! To p re p a re fo r Lesson 5 - 3 , d o Exercises 5 6 - 5 9.
Evaluate each expression.- 6a + 3 for a = 2 57. —2 x - 5 forx = 3 58. |x +2forx= 16
See Lesson 5-1.
55.(1, -2), (-2 , 3)See Lesson 1-2.- 8 - 5 n fo rn = 3
306 C h a p te r 5 Li n ear Fu n ct i o n s