The actual area of a rectangle is 60 Cm2, but while measuring its length a student decreases it by 20% and the breadth increases by 25%. The percentage error in area, calculated by the student is :
A.0.05
B.0.15
C.0.2
D.No change
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3
area of rectangle is length into breadth so let the initial length is a1 and initial breadth is b1 so if we increase the breadth by 25% so it is equal to b2= 5b1/4
and if we decrease a 12 20% so A2 is = 4a1/5
so a1×b1= a2×b2
so no change is there
and if we decrease a 12 20% so A2 is = 4a1/5
so a1×b1= a2×b2
so no change is there
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actual area = 60cm^2
L×B = 60 ---(1)
new length = L - 20% of L
= 0.8L cm
new breadth = B + 25% of B
= 1.25B cm
new area = new length ×new breadth
new area = 0.8L × 1.25B = 1 LB
= 1 × 60 = 60 cm^2
new area = actual area
no change in area .
option (d) is correct. No change.
L×B = 60 ---(1)
new length = L - 20% of L
= 0.8L cm
new breadth = B + 25% of B
= 1.25B cm
new area = new length ×new breadth
new area = 0.8L × 1.25B = 1 LB
= 1 × 60 = 60 cm^2
new area = actual area
no change in area .
option (d) is correct. No change.
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