rrsnathan wrote:
Hi Bunuel,
I have a doubt
In this problem 40% growth is between 4th day and 10th day right? so how come we can multiply the 1.4(for 40 %) to 11+4x, where 11+4X is for 4th day, not the days between the 4ht and 10th.
We should multiply 1.4 to the days between 4th and 10th right?
Please help me in this
We are not comparing growth. We are comparing height.
Initial Height = 11
Constant growth everyday = x
After 4 days, height(H4) = 11 + 4x
After 10 days, height(H10) = 11 + 10x
40% growth between H4 and H10, means:
0.4 = (H10 - H4)/H4
=> 0.4*H4 = H10 - H4
=> 0.4H4 + H4 = H10
=> 1.4*H4 = H10
Substitute values,
1.4*(11+4x) = (11 + 10x)
=> x = 1 (skipped the solving part)
Alternatively,
After 4 days, height(H4) = 11 + 4x
After 10 days, height(H10) = 11 + 10x
Growth = H10 - H4 = (11+10x) - (11+4x) = 6x
% Growth: 6x/(11+4x) = 0.4
=> 6x = 0.4*(11+4x)
=>60x = 4 *(11+4x) = 44 + 16x
=> 44x = 44
=> x = 1