Shortcut:
a1 men and b1 boys can earn Rs Z1 in d1 days, if a2 men and b2 boys can earn Rs Z2 in d2 days, then the following relationship is obtained
men
/
boys
= [
Z1b2d2 − Z2b1d1
/
Z2a1d1 − Z1a2d2
]
Here, a1 = 3, b1 = 4, Z1 = 756, d1 = 7, a2 = 11, b2 = 13, Z2 = 3008, d2 = 8
Putting these values in the shortcut, we get:
men
/
boys
= [
756 x 13 x 8 − 3008 x 4 x 7
/
3008 x 3 x 7 − 756 x 11 x 8
]
= (
78624 − 84224
/
63168 − 66528
)
= (
−5600
/
−3360
)
=
5
/
3
Now, 3m + 4b earn in 1 day = Rs
756
/
7
= Rs 108
or, 3m x 4 x
3
/
5
m earn in 1 day Rs 108
or
27
/
5
m earn in 1 day Rs 108
∴ 1m in 1 day earns Rs
108 x 5
/
27
= Rs 20
Thus, we get that a man earns Rs 20 daily and a boy earns Rs 20 x
3
/
5
= Rs 12 daily
Since, 7m + 9b earn Rs(7 x 20 + 9 x 12) = Rs 248 in 1 day.
∴ 7m + 9b earn Rs 1240 in 5 days.
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