Question

Mary has 21 coins whose total who's total value is 72 shillings. There are twice as many five shilling coins as there are 10 shilling coins. The rest are one shilling coins. What is the number of 10 shilling coins that mary has?

Answer 1

Mary has `3` number of `10` shilling coins.

Explanation:

Let Mary has `x` number of `10` shilling coins , then

Mary has `2 x` number of `5` shilling coins and

Mary has rest `21- (x+2 x)= 21 - 3 x` number of `1` shilling

coins. By given condition , `x *10 + 2 x *5 + (21-3 x)*1 =72`

`:. 10 x + 10 x -3 x = 72 -21 or 17 x = 51 :. x = 51/17 = 3`

Hence Mary has `3` number of `10` shilling coins [Ans]

Answer 2

Mary has `color(magenta)("3 10"` shilling coins

Explanation:

Let the no. of `10` shilling coins she has be `x`

So no. of 5 shilling coins is `2x` and no. of 1 shilling coins is `21-(2x+x)`

Value from:

1 shilling coins `=1(21-3x)=21-3x`

5 shilling coins `=5(2x)=10x`

10 shilling coins `=10(x)=10x`

Total value`=72` shillings

i.e. `color(blue)(21-3x+10x+10x=72` shillings

`-3x+10x+10x=72-21`

`17x=51`

`x=51/17`

`color(darkorange)(x=3`

`therefore` Mary has `color(magenta)("3 10"` shilling coins.