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jek_recluse [69]
3 years ago
10

If a rectangle is altered by increasing its length by 20 percent and its width by 10 percent, its area increases by a percent. W

hat is the value of a?
A) 25
B) 28
C) 30
D) 32
Mathematics
1 answer:
aleksklad [387]3 years ago
5 0

Answer:

D

Step-by-step explanation:

Remember that the formula for the area of a rectangle is:

A=lw

Where l is the our length and w is our width.

If we increase our length by 20%, this means that we add 20% or 0.2 of our old length to our old length. So, our new length will be:

l_{new}=l+.2l

Combine like terms:

l_{new}=1.2l

Similarly, if we increase our width by 10%, this means that we add 10% or 0.1 of our old width to our old width. So, our new width is:

w_{new}=0.1w+w

Combine like terms:

w_{new}=1.1w

Therefore, our new area will be:

A_{new}=(l_{new})(w_{new})

Substitute 1.2l and 1.1w. This yields:

A_{new}=1.2l(1.1w)

Multiply:

A_{new}=1.32lw

Our old area is:

A_{old}=lw

So, our area increased by a factor of 1.32.

This is the same as 32% of our old area.

So, our answer is D.

And we're done!

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