Question

Mark (✓) against the correct answer
(5⁻¹ × 3⁻¹)⁻¹=?

(a) $\frac{1}{15}$
(b) $\frac{-1}{15}$
(c) 15
(d) −15

Answer 1

(c) 15

We have:

${\left(5^{-1}\times 3^{-1}\right)}^{-1}={\left(\frac{1}{5}\times \frac{1}{3}\right)}^{-1}$
= ${\left(\frac{1}{15}\right)}^{-1}$
= ${\left(\frac{15}{1}\right)}^1=15$ $\left[s\mathrm{ince}{\left(\frac{a}{b}\right)}^{-1}={\left(\frac{b}{a}\right)}^1\right]$