Question

A number is first increased by 40% and then decreased by 25%, again increased by 15% and then decreased by 20%. What is the net increase/decrease per cent in the number?
1. 7.2% decrease
2. 6.4% increase
3. 3.4% decrease
4. 3.4% increase

Answer 1

Correct Answer - Option 3 : 3.4% decrease

Let the number be x

⇒ \({\rm{x\;}} \times \frac{{7}}{{5{\rm{\;}}}} \times \frac{{3}}{{4{\rm{\;}}}} \times \frac{{23}}{{20{\rm{\;}}}} \times \frac{{4}}{{5}}\)

⇒ \({\rm{x\;}} \times \frac{{483}}{{500{\rm{\;}}}}\)

⇒ 0.966x

⇒ 0.966x is less than x

 ⇒ Decrease per cent in the number = \(\frac{{{\rm{x}} - 0.996{\rm{x}}}}{{100}} = 3.4{\rm{\% \;}}\)

 ∴ Net decrease per cent in the number is 3.4%