GMAT Math Practice Test #1

Answer B: If length l is increased by 10%, it becomes 1.1 l. Similarly width becomes 1.1 w. Area = length X width = 1.1 l X 1.1 w = 1.21lw. Thus, the area lw increases to 1.21lw. Hence the increase is 21%.

Key takeaway: While multiplying decimal number, be careful in placing decimal at proper place.