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mangamma
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I don't get the solutions. can anyway try solving this using the tetter totter method..
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mangamma
The manufacturing cost of a certain product consists of two parts – production cost and testing cost. In a year, the manufacturing cost increased by 23%, whereas the production and testing costs increased by 25% and 20% respectively. Before the increase, the testing cost was what percentage of the production cost?

A. 25%
B. 33.33%
C. 50%
D. 66.67%
E. 125%

Let's just Plug In The Answers (PITA), avoid any confusion, and minimize the risk of making a silly mistake. I like trying B and D.

B:
T is 33% of P. T = 1 and P = 3. So, M = 4.
T increased to 1.2 and P increased to 3.75. So, M increased to 4.95.
M increased by 0.95/4. That's more than 23% (23% of 4 is 0.92). Wrong.

D:
T is 67% of P. T = 2 and P = 3. So, M = 5.
T increased to 2.4 and P increased to 3.75. So, M increased to 6.15.
M increased by 1.15/5. That's 2.3/10, which is 23%. Yay!!

Answer choice D.


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we can solve it as an alligation, we know that the production and testing have increased by respectively 25 and 20 percent, we know that the total cost has increased by 23%. this means that the 2 costs have different weights initially. to calculate the weights just use the aligation:
Production --> 25-23 = 2
Test --> 23-20 = 3

this means that the ratio between Testing and production is 2/3 --> 66.67%
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M = P+T

The M increased by 23% so M(this year) = M(Previous year) + 23%M(Previous year) = 1.23M which is 1.23(P+T)
same as the P and T:
P(This year) = 1.25P
T(This year) = 1.20T

So now we will get:
1.23(P+T) = 1.25P + 1.2T
1.23P + 1.23T = 1.25P + 1.2T
0.03T = 0.02P

The question ask "Before the increase, the testing cost (T) was what percentage of the production cost (P)":

(T/P) = 0.02/0.03 = 2/3 = 0.6667

It's ask in percent so 0.6667*100 = 66.67%
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