Decimal Fraction - Aptitude MCQ Questions and Solutions with Explanations

$$\eqalign{ & = \frac{1}{4} + \frac{1}{{4 \times 5}} + \frac{1}{{4 \times 5 \times 6}} \cr & = \frac{1}{4}\left( {1 + \frac{1}{5} + \frac{1}{{30}}} \right) \cr & = \frac{1}{4}\left( {\frac{{30 + 6 + 1}}{{30}}} \right) \cr & = \frac{1}{4} \times \frac{{37}}{{30}} \cr & = \frac{{37}}{{120}} \cr & = 0.3083 \cr} $$

Given expression :
(833.25 - 384.45) ÷ 24
= 18.7

Quantity of blood donated in 2 years
= (350 × 3) ml
= 1050 ml
= 1.05 litres
∴ Quantity of blood donated in 6 years
$$ = \left( {\frac{{1.05}}{2} \times 6} \right)$$
= 3.15 litres

Given expression :
51.4 × 8
= 411.2

Given expression :
$$\eqalign{ & \frac{{{{\left( {5.71} \right)}^3} - {{\left( {2.79} \right)}^3}}}{{{{\left( {5.71} \right)}^2} + 5.71 \times 2.79 + {{\left( {2.79} \right)}^2}}} \cr & = \left( {\frac{{{a^3} - {b^3}}}{{{a^2} + ab + {b^2}}}} \right) \cr & = \frac{{\left( {a - b} \right)\left( {{a^2} + ab + {b^2}} \right)}}{{\left( {{a^2} + ab + {b^2}} \right)}} \cr & = \left( {a - b} \right) \cr & = \left( {5.71 - 2.79} \right) \cr & = 2.92 \cr} $$

Given expression :
7777 ÷ 77 ÷ 5
= 101 ÷ 5
= 20.2

Given expression :
$$\frac{{\left( {{a^2} - {b^2}} \right)}}{{\left( {a + b} \right)}}$$  , where a = 3.63, b = 2.37
$$\eqalign{ & = \frac{{\left( {a - b} \right)\left( {a + b} \right)}}{{\left( {a + b} \right)}} \cr & = \left( {a - b} \right) \cr & = 3.63 - 2.37 \cr & = 1.26 \cr} $$

Given expression :
= 7.92 ÷ 0.6
= 79.2 ÷ 6
= 13.2

Given expression :
= 1576 ÷ 45.02 + 23.99 × $$\sqrt {255} $$
= 1575 ÷ 45 + 24 × $$\sqrt {256} $$
= 35 + 24 × 16
= 35 + 384
= 419 $$ \approx $$ 420

$$\eqalign{ & {\left( {\frac{{0.05}}{{0.25}} + \frac{{0.25}}{{0.05}}} \right)^3} \cr & = {\left( {\frac{5}{{25}} + \frac{{25}}{5}} \right)^3} \cr & = {\left( {\frac{1}{5} + 5} \right)^3} \cr & = {\left( {\frac{{26}}{5}} \right)^3} \cr & = {\left( {5.2} \right)^3} \cr & = 140.608 \approx 140.6 \cr} $$