16% of 91.....assuming you cant use a calculator.....lets start easy:
1. We know 10% is 9.1 (Decimal moves 1 spot to the left)
2. We know 1% is .91 (Decimal moves 1 more spot to the left)
3. If 10% is 9.1, we know 5% would be 4.55
9.1+4.55+.91=14.56 inches. or 1' 2.56"
Original 7' 7" + 1' 2.56"= 8' 9.56" or 8' 10"