Page 172 - Start Up Mathematics_8 (Non CCE)

If the saving is ` 30, the total income = ` 100

Ê 100ˆ
If the saving is ` 1, the total income = ` Á Ë 30 ¯ ˜

100
If the saving is ` 2,100, the total income = ` × 2,100 = ` 7,000
30
Hence, Poonam’s total income = ` 7,000
Alternate Method

Let Poonam’s total income be ` x.
25 25x
Money spent on house rent = 25% of x = ` ¥ x = `
100 100

Ê 25 xˆ Ê 100x - 25xˆ 75x
Balance = ` x - 100 ˜ = ` Á Ë 100 ˜ = ` 100
Á
¯
Ë
¯
75x 60 75x 4 500, x 45
Money spent on household = 60% of = ` × = ` = ` x
100 100 100 10 000, 100
75x 45x 30x
Saving = ` – ` = `
100 100 100
Saving given = ` 2,100
30x
fi = 2,100 fi 30 × x = 2,100 × 100
100

2 100 100, ¥
fi x = = ` 7,000
30
Hence, Poonam’s total income = ` 7,000
Example 6: A packet of sweets costs ` 55. This is 10% more than its cost in the previous year. What was
the cost of this packet of sweets in the previous year?
Solution: Let the cost of a packet of sweets in the previous year be ` 100.
Increase in cost = 10% of ` 100 = ` 10
\ Present cost = ` (100 + 10) = ` 110

If present cost is ` 110, previous year cost = ` 100
100
If present cost is ` 1, previous year cost = `
110
100
If present cost is ` 55, previous year cost = ` × 55 = ` 50
110
Example 7: Karishma’s income is 20% less than that of Pooja. How much percent is Pooja’s income more
than that of Karishma’s?
Solution: Let Pooja’s income be ` 100.
Since Karishma’s income is 20% less than that of Pooja,

\ Karishma’s income = ` 80
If Karishma’s income is ` 80, Pooja’s income = ` 100
100
If Karishma’s income is ` 1, Pooja’s income = `
80

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