Ratio and Proportion Flashcards

A wire crew installs 240 feet of conduit in 6 hours. At the same rate, how many feet will they install in 9 hours?

Answer: 360 feet

The rate is 240 ÷ 6 = 40 feet per hour, so in 9 hours they install 40 × 9 = 360 feet.

If 4 electricians can wire 3 apartments in 2 days, how many apartments can 8 electricians wire in 2 days?

Answer: 6

Doubling the number of electricians doubles the output, so 8 electricians wire 3 × 2 = 6 apartments in the same 2 days.

The ratio of copper wire to aluminum wire used on a job is 5:3. If 40 pounds of copper wire is used, how many pounds of aluminum wire are needed?

Answer: 24 pounds

Setting up the proportion 5/3 = 40/x gives x = (40 × 3) / 5 = 24 pounds.

A blueprint is drawn at a scale of 1 inch = 8 feet. If a room measures 3.5 inches on the blueprint, what is the actual length of the room?

Answer: 28 feet

Multiply the blueprint measurement by the scale factor: 3.5 × 8 = 28 feet.

On a job site, the ratio of journeymen to apprentices is 2:5. If there are 14 journeymen, how many apprentices are on the site?

Answer: 35

Setting up the proportion 2/5 = 14/x gives x = (14 × 5) / 2 = 35 apprentices.

If a 12-volt battery is connected to a circuit with a current of 3 amps, and the voltage is increased proportionally to produce 5 amps, what is the new voltage?

Answer: 20 volts

Using the proportion 12/3 = x/5, solving gives x = (12 × 5) / 3 = 20 volts.

A spool of wire contains 500 feet and weighs 15 pounds. How much does a 200-foot section of the same wire weigh?

Answer: 6 pounds

The unit rate is 15/500 = 0.03 lb/ft, so 200 feet weighs 200 × 0.03 = 6 pounds.