Question

$\frac{1}{1\times 4}+\frac{1}{4\times 7}+\frac{1}{7\times 10}+\frac{1}{10\times 13}+\frac{1}{13\times 16}+\frac{1}{16\times 19}$ =

• A. 0.95
• B. 0.33
• C. 0.166
• D. 0.26
• E. 0.4

Answer 1

The correct option is B

0.33

$\frac{1}{1\times 4}+\frac{1}{4\times 7}+\frac{1}{7\times 10}+\frac{1}{10\times 13}+\frac{1}{13\times 16}+\frac{1}{16\times 19}$

= $\frac{1}{3}\times (1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\dots \dots \dots .-\frac{1}{19})$

= $\frac{1}{3}\times (1-\frac{1}{19})=\frac{6}{19}$