# Direct and inverse proportion

So cost of 90 pump = $90\times 500$ = Rs.45000

So total money that Vikash had = Rs.45000

Discount on each pump = Rs.50

So cost of each pump after discount = Rs.500 - Rs.50 = Rs.450

So, number of pumps in Rs.45000 = $\frac{45000}{450}$ = 10

Therefore Vikash can buy 10 pumps.

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