Question

Evaluate $100\times \frac{(0.4{)}^3-(0.24{)}^3}{(0.4{)}^2+0.4\times 0.24+(0.24{)}^2}$ using formula.

Answer 1

$100\times \frac{{0.4}^3-{0.24}^3}{{0.4}^2+\left(0.4\right)\left(0.24\right)+{0.24}^2}$

$=100\times \frac{{(0.4-0.24)[0.4}^2+\left(0.4\right)\left(0.24\right)+{0.24}^2]}{{0.4}^2+\left(0.4\right)\left(0.24\right)+{0.24}^2}$ ...$[a^3-b^3={(a-b)[a}^2+ab+b^2]$

$=100\times (0.4-0.24)=0.16\times 100=16$