Question

16 Sara had some 2-rupee and 5-rupee coins
in her money box. She exchanged them
for some 10-rupee coins. If the number of
5-rupee coins is one less than the number
of 2-rupee coins, then find the number of
5-rupee coins.​

Answer 1

If Sara had exchanged the coins to get coins of 10 Rs, this implies that the number of 2 rupee coins has to be a multiple 5.

But we know that x cant be even as  when x is even the sum of the value  number in Rs is not divisible by 10.

Thus the number of 2 rupee coin = 5x

Thus the number of 5 rupee coin = 5x-1

(where x i a natural number and odd)

Answer 2

Answer:

Let the number of 2-rupee coins be x.

Then, the number of 5-rupee coins will be x - 1

Total amount of 2-rupee coins = ₹2 * x

= ₹2x

Total amount of 5-rupee coins = ₹5 * ( x-1 )

= ₹5x - 5

Total amount in money box = ₹2x + ( ₹5x - 5 )

= ₹ 7x -5

{ if we have to make this amount a multiple of 10 then ₹2 's quantity should be a multiple of 10, and the quantity of ₹5 should be even to be a multiple of 10 }

Therfore, the quantity of ₹2 coins can be 5  (₹2 * 5 = ₹10, a multiple of 10)

and

₹5 coins is 1 less than the quantity of ₹2 coins so

The number of ₹ 5 coins will be  = (5 - 1)

=  4

{ checking, (₹2 * 5) + (₹5 * 4) = ₹10 + ₹20 = ₹30

and ₹ 30 is a multiple of 10 }

please mark it as Brainliest

Step-by-step explanation: