Correct Answer - Option 3 : Rs. 117
Work done ratio of a man, a woman and a child = 3 : 2 : 1
Total work done by 20 men, 30 women and 36 children in 1 week = 3 × 20 + 2 × 30 + 1 × 36
= 60 + 60 + 36 = 156 unit
156 unit = Rs. 78
1 unit = 78/156 = Rs. 1/2
Total work done by 15 men, 21 women and 30 children in 2 week = [3 × 15 + 2 × 21 + 1 × 30] × 2 = [45 + 42 + 30] × 2 = 117 × 2 = 234
234 unit = 234 × (1/2) = Rs. 117