Sudhanshuacharya wrote:
tracyyahoo wrote:
The cost C of manufacturing a certain product can be estimated by the formular C=0.03rs(t^2), where r and s are the amounts, in pounds, oof the two major ingredients and t is the production time in hours. If r is increased by 50%, s is increased by 20%, and t is decreased by 30%, by approximately what percent will the estimated cost manufacturing the product change?
a) 40% increase
b) 12% increase
c) 4% incease
d) 12% decease
e) 24% decrease
pls explain me, thank you. I need it.
From the formula we deduce that C directly proportional to r, s and t^2
hence an increase or decrease in these values will directly change the value of C by that factor
There new r => 1.5r
new s => 1.2s
new t^2 = (0.7t)^2 = .49t^2
let the constant 0.03 be termed as A
Putting these new values: C1 = A*1.5r*1.2s*.49t^2
C1 = 0.882A*r*s*t^2 = 0.882(C)
There the net value decrease by 12% approx
Hence D
I am using the same approach as above:
50% increase = 1.5r
20% incease = 1.2s
30% decrease = .7r
So new value = (1.5r)(1.2s)(.7r)^2=(15/10*12/10*49/100)(.03rst^2)
Old value = (.03rst^2)
Now I am approx. 49 to 50 for faster calculation -
New value = (15/10*12/10*50/100) = 180/100*1/2=(90/100)(.03rst^2)
New value is 90% of the old value
So 10% less ....Let me see any value near 10% decreases
B is the closest...So I go with B