Question 30

The ratio of sand to gravel in a mixture is 7 : 8 while that between gravel and cement is 6 : 7. What is the ratio of sand to cement in the mixture?

Solution

Given

Sand:gravel = 7 : 8 .....eq1

gravel : cement:6 : 7......eq2

multiply eq 1 by 3 & eq by 4 we get

Sand:gravel = 21 : 24 eq 3

gravel : cement:24 : 28 eq 4

in eq 3 and 4 quantity of gravel is same so we can say that

sand:gravel:cement= 21:24:28

from this

sand=cement= 21:28=3:4

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