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Byju's Answer
Standard X
Mathematics
Elimination Method of Finding Solution of a Pair of Linear Equations
If 7 pens a...
Question
If
7
pens and
3
books cost
R
s
1395
, while
5
pens and
4
books cost
R
s
1665
. Find the cost of a book
A
360
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B
45360
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C
35350
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D
n
o
n
e
o
f
t
h
e
s
e
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Solution
The correct option is
A
360
Let the cost of
1
pen be
x
and the cost of
1
book be
y
Then
7
x
+
3
y
=
1395
-----
(
1
)
×
4
5
x
+
4
y
=
1665
−
−
(
2
)
×
3
4
×
(
1
)
--------
3
×
(
2
)
(
28
x
+
12
y
)
−
(
15
x
+
12
y
)
=
5580
−
4995
13
x
=
585
x
=
45
Putting
x
=
45
in (1)
7
×
45
+
3
y
=
1395
⇒
315
+
3
y
=
1395
⇒
3
y
=
1395
−
315
⇒
3
y
=
1080
⇒
y
=
360
Therefore Cost of one pen is Rs
45
and cost of one book is Rs
360
Suggest Corrections
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Similar questions
Q.
The total cost of 6 books and 7 pens is 79 rupees and the total cost of 7 books and 5 pens is 77 rupeess. Find the cost of 1 book and 2 pens.
Q.
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5
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Q.
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Q.
The cost of
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