a person spent 564 in buying pens and pencils if cost of each pen is 7 and each pencil is 3 and if the total no. of tngs bought was 108, how many of each type did he buy ?
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Let no if pens bought be x
Let no of pencils bought be y
7x + 3y = 564 -------- Eq 1
x + y = 108 -------- Eq 2
Multiplying Eq 2 by 3 and subtracting it from Eq 1
7x + 3y = 564 -------- Eq 1
3x +3 y = 324 -------- Eq 2 (multiplied by 3)
(-) (-) (-)
-----------------------
4x = 240
x = 240/4 = 60 pens
Subtituting the value of x in eq 2
60 + y = 108
y = 108-60 = 48 pencils
Let no of pencils bought be y
7x + 3y = 564 -------- Eq 1
x + y = 108 -------- Eq 2
Multiplying Eq 2 by 3 and subtracting it from Eq 1
7x + 3y = 564 -------- Eq 1
3x +3 y = 324 -------- Eq 2 (multiplied by 3)
(-) (-) (-)
-----------------------
4x = 240
x = 240/4 = 60 pens
Subtituting the value of x in eq 2
60 + y = 108
y = 108-60 = 48 pencils
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