Title?
Work Example ?

ACT Work Keys Level: 7

Problem:

How fast will a car be traveling at 3000 rpm in

Given:
3rd gear ratio:
4th gear ratio:
5th gear ratio:
Rear axle:
Tire diameter:
1 mile: 		1.25 : 1
1 : 1
0.7 : 1
3.73 : 1
25 inches
5280 feet


Solution:

Engine-to-transmission ratio is 1.25 : 1.

So, , 3000 = 1.25 t, or = t = 2400 rpm transmission.

Transmission-to-rear axle ratio is 3.73 : 1.

So, , 2400 = 3.73 RA or = RA = 643 rpm rear axle.

Revolutions/hr: 643 rpm × 60min/hr = 38,600 rev/hr

Tire circumference: 25 inches × 3.14 = 78.5 inches

Speed: 38,600 rev/hr × 78.5 = 3,030,000 inches/hr

Speed: 3,030,000 inches/hr ÷ 12 in/ft = 252,000 ft/hr

Speed: 252,000 ft/hr ÷ 5280 ft/mile = 47.8 miles/hr
4th Gear: 59.8 mph
5th Gear: 85.4 mph