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ML Aggarwal Solutions Class 9 Mathematics Solutions for Problems on Simultaneous Linear Equations Exercise 6 in Chapter 6 - Problems on Simultaneous Linear Equations
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A man has certain notes of denominations Rs. 20 and Rs. 5 which amount to Rs. 380. If the
a number of notes of each kind is interchanged, they amount to Rs. 60 less as before. Find the
a number of notes of each denomination.
Let’s consider the number of 20 rupee notes to be x
And the number of 5 rupee notes be y
Then, according to the given conditions we have
20x + 5y = 380 … (i) and
5x + 20y = 380 – 60
⇒ 5x + 20 y = 320 … (ii)
Now, multiplying (i) by 4 and subtracting with (ii) we get
80x + 20y = 1520
5x + 20 y = 320
(-)--(-)----(-)-------
75x = 1200
x = 1200/75
x = 16
On substituting the value of x in (i), we get
20(16) + 5y = 380
320 + 5y = 380
5y = 380 – 320 = 60
y = 60/5
y = 12
Therefore, the number of 20 rupee notes = 16 and the number of 5 rupee notes = 12
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