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Sunday, March 3, 2013

Civil Service Commission Professional or Sub-Professional Reviewer - Page 116/159

Mathematics Test V Solution - Page 116

46. If 8 men can plant 288 trees in one day, how many trees can 12 men plant in 5 days?

Let N - be the number of trees

N =       288 trees    x 12 men x 5 days    ----->  288 x 12 x 5
        8 men - 1 day                                                   8          trees

N = 2, 160 trees * Ans.


47. If the length of a rectangle is increased by 25% and its width is decreased by 20%, what happens to the area of the triangle?

Aorig. = LW

Anew = L (1+0.25) x W (1 - 0.20)
         = L (1.25) x W (0.8)              -----> (1.25) (0.8) LW
Anew = 1 x LW
Anew = Aorig.

therefore, no change in the area * Ans.

48. The formula for the volume of a sphere is V = 4/3 πr3. If the radius (r) is tripled, what will be the ratio of the new volume to the original volume?

Vorig. = 4/3 πr3

Vnew = 4/3 π(3r)3              ----->   = 4/3 π(27r3)        ------> 27 (4/3  πr3)
Vnew = 27 Vorig.                ----->   Vnew : Vorig.   =  27 : 1 * Ans.

49. The scale on a map is 1 : 8. If a surveyor reads a certain measurement on the map as 4.6 cm instead of 5.0 cm, what will be the resulting approximate percent error on the full size model?

% error =   error   x 100% ->   5.0 - 4.6  x 100% -> 0.4 x 100% -> 8% *Ans.
              correct value                  5.0                                5

50. In a certain recipe, 225 grams of beef are called for to make 6 servings. If Mrs. Alferez wants to use the recipe for 8 servings, how many grams of beef must she use?

Let N - be the number of grams required

225 : 6 = N : 8

6N = 8(225)
6N = 1800
N   = 1800 / 6
N   = 300 grams. * Ans.

Civil Service Reviewer Post 116/159