help pls!!!

[swapna.rajanish7]

If cement,gravel and sand are to be mixed in the ratio 3:5:7 respectively and 5 tons of cement are available, how many tons of mixture can be made?(Assume there is enough gravel and sand available to use all the cement)
15
20
25
30
75

ans is c...some one help??

[abhisec]

The ratio is 3:5:7.

so assume x is the multiplier, therefor total mixture will be 3x + 5x + 7x = 15x.

It is given cement is 5 tonnes or 3x = 5.

Therefore x = 5/3.

total mixture = 15 * 5/3 = 25.

[rajkapoor]

simple way to think about this questions is
taking the current ratio into account,following can be dervied -

if cement is 3, then the total mixture is (3+5+70 = 15
if cement is 1 , then total mixture will be 15/3 = 5
if cement is 5 , then total mixture will be 5*5 = 25 (answer choice c)

[Ben Ku]

Please cite the source (author) of this problem. We cannot reply unless a source is cited (and, if no source is cited, we will have to delete the post!). Thanks.