Which of the Following Is an Example of Using a Buildup

Multiple Choice

Which of the following is an example of using a buildup strategy method of solving proportions?

A) Allison bought 3 pairs of socks for $12.To find out how much ten pairs cost,find that $12 divided by 3 is $4 a pair,and multiply $4 by 10 for a total of $40.
B) A square with a length of 2 inches was enlarged by a scale factor of 4 and is now 8 inches long.
C) If 5 candy bars cost $4.50,then 10 would cost $9.(Because 5 × 2 = 10,multiply $4.50 by 2) .
D) If 23= x15 ,find the cross products,30 = 3x,and then solve for x.x = 10.