Percents, pay, and flow

Percent means per hundred. 15% is 0.15. Of means multiply. 15% of 260 is 0.15 × 260.

A fast path: 10% is the number with the decimal moved one place. 10% of 260 is 26. 5% is half of that, 13. So 15% is 39.

Hourly pay is hours × rate. Do that for each person before you compare. A higher rate can still pay less if the hours are short. Flow works the same way. Gallons = gallons per minute × minutes. Minutes = gallons ÷ gallons per minute.

An average is the total divided by how many items. Read the stem. Total and average are different questions.

A ratio such as 4:1 means 4 of the first thing for 1 of the second. A 4:1 gear reduction turns the output once while the input turns four times. A proportion keeps that same relationship when the job gets bigger: if 5 bolts weigh 10 ounces, 15 bolts weigh 30 ounces.