Hello,

Let the amount of work done by brother in one day be x.

So, work done by Navya in one day is 1.6x.

So, amount of work done in one day together is x + 1.6x = 2.6x

(i) Therefore, fraction of work done by Navya is 1.6x / 2.6x = 0.61 or 61%

(ii) If Navya alone can complete work in 65 days, then total work is = 1.6x * 65 =104x.

If both of them work together, number of days taken is = 104x / 2.6x = 40 days.

Hope this helps.

Comment for more clarification.

Thanks.