Question

i have a total of rs.300 in coin of denomination rs.1, 2 and 5 .the number of rs. two coins is three times the number of five coins . the total number of coin is 160. how many coin of each denomination are with me

Answer 1

first  let let the no. of rs 5 coins be x

& the no. of rs 1 coin be y

& no. of rs 2 coins be 3 x

a.q.t total no. of coins = 160

x + 3x+y = 160

4x + y = 160 eq. 1

again a.q.t total rs = 300

5x + 2(3x) + 1y = 300

11x + y = 300 eq. 2

by elimination method

on subtracting both the equations

4x + y = 160

-11x -y = -300

=-7x =-140

  x =20

on putting the the value of x in eq 2

4(20) + y =160

80 + y = 160

y =80

now,

no of rs 2 coins = 3(20)

                      = 60

no. of rs 5 coins = 20

no. of rs 1 coins=80

Answer 2

let no of rs5 coins X,cost=5X
no of rs2coins be3X,cost=6X
let no of rs1 coins beY,cost=y
now,
total coins=3X+X+Y
160=4X+Y.......eq1
again,
total cost=6X+5X+Y
300=11X+Y........eq2

now you can find the value of X and Y .