Mr. Manohar gave 20% of his income to his elder son and 30% to his younger son. He gave 10% of the balance income as donation to a school.

Let the income of Mr. Manohar be ₹ x.

. Amount given to elder son = 20% of x

 Amount given to younger son = 30% of x 

Total amount given to both sons = (20 + 30)% of x =50% of x 

∴ Amount remaining with Mr. Manohar = (100 – 50)% of x

 = 50% of x 50 

= \(\frac{50}{100}\)× 100 

= 0.5 x 

He gave 10% of the balance income as donation to a school.

 Amount donated to school = 10% of 0.5x 

= \(\frac{10}{100}\) × 0.5x

 = 0.05x 

∴ Amount remaining with Mr. Manohar after donating to school = 0.5x – 0.05x 

= 0.45x

 Mr. Manohar still had 1,80,000 for himself after donating to school.

 ∴ 180000 = 0.45x

∴ \(x = \cfrac{180000}{0.45} \) = \( \cfrac{180000\times100}{0.45\times 100} \) = \(\cfrac{18000000}{45} \) = 400000

∴ The income of Mr. Manoliar is ₹4,00,000.