Evaluate (5^2 - 3^3)/(7^-1).

Evaluate $\frac{5 ^{2} - 3 ^{3}}{7 ^{- 1}}$ .

hard 4 marks Class 8 · Mathematics · Exponents and Powers

Answer

-14

The correct answer is -14 — Divide $- 2$ by $\frac{1}{7}$ , which is equivalent to multiplying by 7: $- 2 \times 7 = - 14$ .

Compute $5^{2} = 25$ .
Compute $3^{3} = 27$ .
Subtract to get the numerator: $25 - 27 = - 2$ .
Compute $7^{- 1} = \frac{1}{7}$ .
Divide $- 2$ by $\frac{1}{7}$ , which is equivalent to multiplying by 7: $- 2 \times 7 = - 14$ .

Common mistake: not converting

7^{- 1}

\frac{1}{7}

Concept tested: Negative exponent in denominator