Question

A school has enough food for 400. children for 12 days. How long will the food last if 80 more children join them?

Answer 1

Let X1=400
      Y1=12
      X2=400+80=480
      Y2=?
here , no.of children and no.of days are in inverse proportion
        so,X1/X2=Y2/Y1
         =)400/480=Y2/12
         =)Y2/12=5/6
         =)Y2=5*2
         =)Y2=10
 therefore,if 80 more children join them then the food will last for 10 days.            

Answer 2

400 children have food for 12 days
Therefore, 1 child has food for 12 × 400 days
Therefore, 400 + 80 = 480 children have food for (12 × 400)/480 days
                                                                             = 40 ÷ 4
                                                                             = 10 days
Therefore, the food will last 10 days if 80 more people join them.

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