Bluebook SAT Test Ratios, Rates, Proportional Relationships, and Units 10

Question 1

Two pipes together fill a tank in 6 hours. Pipe A alone fills it in 10 hours. How many hours does Pipe B alone take to fill the tank?

Accepted Answer

15 hours

Answer

Combined rate = 1/6; Pipe A rate = 1/10; Pipe B rate = 1/6 − 1/10 = 5/30 − 3/30 = 2/30 = 1/15, so Pipe B takes 15 hours.

Question 2

A car uses 6 liters of fuel per 100 km. If fuel costs $1.80 per liter, how much does it cost to drive 350 km?

Accepted Answer

$37.80

Answer

Fuel used = 350 × (6/100) = 21 liters; cost = 21 × $1.80 = $37.80.

Question 3

In a poll, 3 out of every 8 people prefer brand X. If 2,400 people were polled, how many preferred brand X?

Accepted Answer

900

Answer

3/8 × 2,400 = 900 people.

Question 4

A 250 g packet of rice costs $1.50 and a 750 g packet costs $4.20. How many cents per 100 g cheaper is the larger packet?

Accepted Answer

4 cents

Answer

250 g packet: 150/250 × 100 = 60 cents per 100 g; 750 g packet: 420/750 × 100 = 56 cents per 100 g; difference = 4 cents per 100 g.

Question 5

A worker is paid $22 per hour. After taxes of 25%, what is the worker's take-home pay for a 35-hour week?

Accepted Answer

$577.50

Answer

Gross pay = 35 × $22 = $770; tax = 25% × $770 = $192.50; take-home = $770 − $192.50 = $577.50.

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