There are 400 cardboard boxes in a truck .Total mass is 3540 kkg.The mass of one large box is 12 kg and mass of small one is 5kg.Ratio of no. of large boxes to small boxes?

Answer:

Let ,Total number of large boxes  =  x
And
Total number of small boxes  =  y

So, from first condition , we get

x  + y  =  400  ---------------- ( 1 )
And
From second condition , we get
12x  + 5y  =  3540  ------------------ ( 2 )

Now we multiply by 5 in equation 1 , and get

5x  + 5y  =  2000  ------------------- (  3 )

Now we subtract equation 3 from equation 2 , and get

7x  =  1540

x  =  220 , Substitute that value in equation 1 , we get

220 + y =  400

y  =  180
So ,
Total number of large boxes  = 220
And
Total number of small boxes  = 180
Then
$\frac{Total large boxes}{Total small boxes} = \frac{220}{180} = \frac{11}{9}$ , So

Total number of Large boxes  :  Total number of Small boxes  =  11 :  9  ( Ans )