Question

Tick (✓) the correct answer
The value of (3⁻¹ + 4⁻¹)⁻¹ ÷ 5⁻¹ is
(a) $\frac{7}{10}$
(b) $\frac{60}{7}$
(c) $\frac{7}{5}$
(d) $\frac{7}{15}$

Answer 1

(b) $\frac{60}{7}$

${\left(3^{-1}+4^{-1}\right)}^{-1}÷5^{-1}={\left(\frac{1}{3}+\frac{1}{4}\right)}^{-1}÷\frac{1}{5}={\left(\frac{4+3}{12}\right)}^{-1}÷\frac{1}{5}={\left(\frac{7}{12}\right)}^{-1}÷\frac{1}{5}=\left(\frac{12}{7}\right)÷\frac{1}{5}=\frac{12}{7}\times 5=\frac{60}{7}$