(solved)Question 18 SSC-CGL 2020 March 3 Shift 1

Length of a rectangle is increased by 40%, and the breadth reduced by 20%. Find the percent change in the area?

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Parveen,

Question 18
SSC-CGL 2020 Mar 3 Shift 1

Length of a rectangle is increased by 40%, and the breadth reduced by 20%. Find the percent change in the area?

Solution in Brief

Take both length and breadth as 10 each. Area = 100. New length = 14, new breadth is 8, so new area is 14x8 = 112, and percent change is 12% answer!

Alternate Solution in Brief

REMEMBER: if % change in length is p, and in breadth b, then the percent change in area is p + q + pq/100

∴ % change by shortcut is:

40 + (-20) + [40 x (-20)]/100 = 12% Ans!

Solution in Detail

Let Length = L, Breadth = B

$\displaystyle \therefore$ area A = LB

New length is L + 40% = 1.4L

New breadth is B - 20% = 0.8B

New area 1.4L x 0.8B = 1.12LB

$\displaystyle \therefore \%\text{-change is }$

$\displaystyle = \frac{1.12LB - LB}{LB} \times 100$

which is = 12% answer!

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