Question

A person earns three rupees on the first day. If he earns double every next day, what will be his earning at 10th day.

• A. Rs. 768
• B. Rs. 1536
• C. Rs. 3072
• D. Rs. 30

Answer 1

The correct option is B Rs. 1536

Sol: Given,

First day earning (a)= 3Rs

And he earns double every next day.

To find: The 10th day earning

From given,

Second day earning $=2a=b=6=3(2{)}^{2-1}$

Third day earning $=2b=c=12=3(2{)}^{3-1}$

Fourth day earning $=2c=d=24=3(2{)}^{4-1}$

nth day earning $=3(2{)}^{n-1}$

Thus earning of 10th day will be

10th day earning $=3(2{)}^{10-1}$

$=3(2{)}^9$

$=153$Rs

Therefore 10th day earning will be $1536$ Rs