SOLUTION: Out of 40 children some pay Rs 5 each while the rest contribute Rs 10 for an excursion. If the total collection is Rs 320 how many gave Rs 5?

Question 1010639: Out of 40 children some pay Rs 5 each while the rest contribute Rs 10 for an excursion. If the total collection is Rs 320 how many gave Rs 5?
Answer by ikleyn(52814) (Show Source): You can put this solution on YOUR website!
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Out of 40 children some pay Rs 5 each while the rest contribute Rs 10 for an excursion. If the total collection is Rs 320 how many gave Rs 5?
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One can solve the problem by reducing it to a system of two equations or to a single equation.

More elegant way is to use the common sense and mental math.

Let us assume for a minute that everybody contributed Rs 10.
Then the total collection would be 40*10 = Rs 400, which is in RS 80 more than Rs 320.
It is clear that the difference arose because some children payed Rs 5 that we intently counted as Rs 10.
It is also clear that the number of those who payed Rs 5 is = = 16.

It gives the answer: 16 children payed Rs 5 and 40-16 = 24 payed Rs 10.

For more problems similar to this one see the lesson What type of problems are these? in this site.

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