The perimeter of a rectangle is 50 cm and its length is 15 cm. Using P = 2(l + w), what is its width?
Correct answer: B. 10 cm
Substitute: 50 = 2(15 + w), so 25 = 15 + w and w = 10 cm. Check: 2(15 + 10) = 50. Dividing both sides by 2 first, before subtracting, keeps the numbers small.
easy