Question

Kent has 20 pieces of 50 sen and 20 sen coins.The total value of the coins is RM6.10.

How many 50 sen coins does he have?​

Answer 1

the number of 50sen coins:

x = 7

Explanation:

Taking the number of 50sen coins as x

50(x)

∴ the number of 20sen coins is 20-x (as total no. of coins are 20)

20(20-x)

total amount = 6.10RM = 610sen

equating:

50x + 20(20-x) = 610

50x + 400-20x = 610

50x - 20x = 610-400

30x = 210

x = 210/30 = 7

Therefore, the number of 50sen coins is 7

20sen coins is 20-7= 13.

verification=

50*7 + 20*13 = 610

310 + 260 = 610

610sen = 610sen

6.10RM = 6.10RM

L.H.S = R.H.S

hence, verified.

Answer 2

Number of 50sen coins = 13

Explanation:

Let the number of 50sen coins be = x

Let the number of 20sen coins be = y

Total coins = 20

x + y = 20 ----------------------(i)

Value of 50sen coins = 0.50*x = 0.50x

Value of 20sen coins = 0.20 *y = 0.20y

Total value = RM 6.10

0.5x + 0.2y = 6.10 -------------------(ii)

Multiply (i) by (-0.5) and then add the equations. So, x will be eliminated and we can find the value of y

(i) * (-0.5) -0.5x - 0.5y = -10

(ii) 0.5x + 0.2y = 6.10 { add and now x will be eliminated}

- 0.3y = -3.90

Divide both sides by (-0.3)

y = -3.90/-0.3

y = 13

Plug in the value of y in equation (i)

x + 13 = 20

Subtract 13 from both sides

x = 20 -13

x = 7

Number of 50sen coins = 13