A rectangle has a length and a width , where . If the width, , is increased by , which one of the following statements is correct for all values of and ?
C
Step-by-Step Solution
Insight: Area is the product of length and width; a percentage change in only one dimension translates directly to the exact same percentage change in the area, regardless of the other dimension.
Exam route: Multiply the original area by the width multiplier (1.1) to get the new area. The factor is 1.1, meaning a 10% increase.
Learning route:
- Identify the original dimensions: Length = , Width = . Original Area = .
- Identify the change: Width is increased by 10%, so the new width is . Length remains .
- Calculate the new area: .
- Calculate the percentage change in area:
- Verify other options to be absolutely sure:
- Perimeter: Old = , New = . Increase is , which is not 10% of .
- Diagonal: Old = , New = . The increase is not a flat 10%.
- Square: , but is not guaranteed to equal .
The correct statement is that the area increases by 10%.