Correct Answer - Option 4 : 10 hours

**Given:**

The Ruchi can write a book = 22 days

The Ruchi working = 5 hours per day

**Formula used:**

\({H_1\ × D_1\ × M_1 \over W_1}\ =\ {H_2\ × D_2\ × M_2\over W_2}\) (Where H = The hours, D = The days, M = The number of men and W = The work)

**Calculation:**

Let us assume he will work for X hours per day to complete the work in 11 days

⇒ 5 × 22 = X × 11

⇒ The Ruchi will work each day = X = 10 hours

**∴ The required result will be 10 hours.**

Work = Efficiency × Time