Question

Please explain this underlined part

Answer 1

since

A2= 4 × A1,

then

A2 / A1 = 4 ------------eq(1),

now % increase in Area= (final area-initial area)/initial area × 100,

=(A2 - A1)/A1 × 100,

since A1 is the denominator part of both then we can write it as

= % increase in Area = (A2/A1 - A1/A1) × 100,

= (A2/A1 - 1) × 100,

now put the value of A2/A1 from eq(1), We get

= (4-1) × 100,

= 3×100,

=300%,


A short approach to deal that type of questions):-

% increase in Area = (n²-1)×100%,

where
n= number of times of the side,

mean if the side is doubled
then
n=2,

therefore

% increase in Area = (2²-1)×100%,

=(4-1)×100%,

=3×100=300%,

if each side is triple then n=3,

hence

% increase in Area=(3²-1)×100%,

=(9-1)×100,

=800%

Answer 2

Answer:

800% is answer dear friend