A number is first increased by 10% and then decreased by 10%. The number so obtained is 80 less than the original number. The original number is

Correct option is A

Given:

A number is first increased by 10% and then decreased by 10%.

The final number obtained is 80 less than the original number.

Find the original number.

Solution:

Let the original number be x.

After +10% and −10%:

Final value = $$x\left(1+\frac{10}{100}\right)\times\left(1-\frac{10}{100}\right)$$ = 0.99x

Given:

x - 0.99x = 80

0.01x = 80

x = 8000

Alternate Solution (Exam Trick):