Q 01/05

Which property lets you compute 7 × 98 as 7 × 100 minus 7 × 2, the shortcut behind much mental arithmetic?

A) Associative

B) Distributive

C) Identity

D) Inverse

Answer · why

B) Distributive

Distributive multiplication over subtraction, a(b − c) = ab − ac, is the trick behind mental arithmetic like 7 × 98 = 700 − 14 = 686.

Q 02/05

What is (−8) × (−6), a product that trips up anyone who expects two negatives to stay negative?

A) −48

B) 48

C) −14

D) 14

Answer · why

B) 48

48 is the answer because the product of two negative numbers is positive, which is why squaring any negative number gives a positive result.

Q 03/05

What is the longest side of a right triangle with shorter sides 5 and 12, a classic whole-number triple?

A) 13

B) 17

C) 60

D) 169

Answer · why

A) 13

13 completes the 5-12-13 triple: 5² + 12² = 169, and the square root of 169 is 13. Adding the legs gives 17, a common slip.

Q 04/05

What is 7⁰, the value every nonzero number takes when raised to the power zero?

A) 0

B) 1

C) 7

D) 49

Answer · why

B) 1

1 is the value of 7⁰ because each drop of one in the exponent divides by 7: 7² = 49, 7¹ = 7, and 7 ÷ 7 = 1.

Q 05/05

What is 30% of 70, the discount on a $70 jacket in a sale that takes 30 percent off?

A) $40

B) $49

C) $21

D) $100

Answer · why

C) $21

$21 comes from 0.30 × 70; the sale price is then $49, which is 70% of the original, the shortcut cashiers use instead of subtracting.