PE 1 - Ratio | Arithmetic - Ratio, Proportion & Variation
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The monthly incomes of A and B are in the ratio of 3 : 2 and their expenditures are in the ratio of 5 : 3. Each saves Rs. 1000 a month; find their incomes.
- (a)
1000, 2000
- (b)
2000, 4000
- (c)
6000, 4000
- (d)
None of these
Answer: Option C
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Explanation :
Income : Ai/Bi = 3/2 Expense : Ae/Be = 5/3
Also, Ai - Ae = 1000; Bi - Be = 1000.
If I is the combined income and E the combined expense, then,
Ai = 3/5 × I, Ae = 5/8 × E, Bi = 2/5 × I, Be = 3/8 × E
It is given that, 3/5 × I - 5/8 × E = 1000 …(i)
2/5 × I - 3/8 × E = 1000 …(ii)
Solving (i) and (ii) simultaneously, E = Rs. 8,000 and I = 10,000
∴ Ai = 3/5 × 10,000 = Rs. 6,000 and Bi = 10,000 -6,000 = Rs. 4,000.
Hence, option (c).
Workspace:
A purse contains 144 coins comprising one rupee, 50 paise and 25 paise coins, their values being in the ratio 10 : 15 : 8. Find the number of 25 paise coins.
Answer: 64
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Explanation :
Let's assume the bag has Rs. 33x (∵ 10 + 15 + 8 = 33).
The value of one-rupee coins ⇒ Rs. 10x i.e. 10x coins
The value of 50ps. coins ⇒ Rs. 15x i.e. 30x coins
The value of 25ps. coins Rs. 8x i.e. 32x coins
⇒ 10x + 30x + 32x = 144
⇒ 72x = 144
⇒ x = 2
∴ Number of 25ps. coins is 32x = 64
Alternately,
Ratio of number of coins = value/(face value)⇒Ratio of number of coins of 1 rupee, 50 paise, 25 paise =
10/100 : 15/50 : 8/25 = 10 : 30 : 32
∴ Number of 50 paise coins = (32(144))/(10 + 30 + 32) = 64
Hence, 64.
Workspace:
In a class, 3/5th of the students are girls and 1/3rd of them travel to school by bus, 36 girls of that class do not travel to school by bus. Find the strength of the class.
Answer: 90
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Explanation :
Let the strength of the class be x.
Number of girls = 3/5 × x∙
1/3rd of the girls travel to school by bus.
∴ 2/3rd of them do not travel to school by bus.
⇒ x × 3/5 × 2/3 = 36
⇒ x = 90
Hence, 90.
Workspace:
If and , then find .
- (a)
3/7
- (b)
5/8
- (c)
5/11
- (d)
3/2
Answer: Option C
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Explanation :
Given that a/b = 2/1 and p/q = 3/2
a = 2b and p = 3/2 q
∴ = = =
Hence, option (c).
Workspace:
If X : Y = 4 : 3, find the ratio .
- (a)
7 : 9
- (b)
2 : 3
- (c)
5 : 11
- (d)
11 : 13
Answer: Option C
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Explanation :
X/Y = 4/3
⇒ X= 4Y/3
⇒ X2 = (16Y2)/9
Then, or 5 : 11.
Hence, option (c).
Workspace:
The ratio of the present ages of Akanksha and Netra is 2 : 1. 8 years hence, Netra would be as old as Akanksha is now. Find the present ages (in years) of Netra and Akanksha respectively.
- (a)
8, 16
- (b)
16, 8
- (c)
7, 3
- (d)
3, 7
Answer: Option A
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Explanation :
Given that, the ratio of the ages of Akanksha and Netra is 2 : 1.
Let their ages be 2x and x.
After 8 years Netra's age is equal to the present age of Akanksha.
So, x + 8 = 2x
⇒ x = 8.
Ages of Netra and Akanksha are 8 and 16 years respectively.
Hence, option (a).
Workspace:
x + 2y – 3z = 0 and 2x – 3y – 5z = 0. Find x : y : z.
- (a)
10 : 5 : 1
- (b)
1 : 1 : 1
- (c)
7 : 19 : 1
- (d)
19 : 1 : 7
Answer: Option D
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Explanation :
x + 2y – 3z = 0 …(1)
2x – 3y – 5z = 0 …(2)
(1) × 2 – (2)
7y = z
Substituting z = 7y in equation (1).
x + 2y – 21y = 0
⇒ x = 19y
∴ x : y : z = 19y : y : 7 = 19 : 1 : 7
Hence, option (d).
Workspace:
What must be added to both the terms x and y so that their ratio becomes equal to p : q?
- (a)
- (b)
- (c)
- (d)
Answer: Option C
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Explanation :
Let the required quantity be t
(x + t) : (y + t) = p : q
⇒ (x + t)q = (y + t)p
⇒ xq + qt = yp + pt
⇒ (p – q)t = xq – yp
∴ t = (xq - yp)/(p - q)
Hence, option (c).
Workspace:
Divide Rs. 375 among A, B and C so that if Rs. 4, Rs. 5, Rs. 6 be subtracted from their respective shares, the remainder may be in the ratio 3 : 4 : 5.
- (a)
175, 125, 75
- (b)
120, 125, 130
- (c)
94, 125, 156
- (d)
90, 125, 160
Answer: Option C
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Explanation :
Let us find the share of the remainder money amongst A, B and C. Then, since remainder money = 375 – (4 + 5 + 6) = 360
A’s remainder share = 3/12 × 360 = 90
B’s remainder share = 4/12 × 360 = 120
C’s remainder = 5/12 × 360 = 150
Thus,
A’s share = Rs. 90 + Rs. 4 = Rs. 94
B’s share = Rs. 120 + Rs. 5 = Rs. 125
C’s share = Rs. 150 + Rs. 6 = Rs. 156
Hence, option (c).
Workspace:
For which of the following values of a : b is (4a2 + 2ab) : (2ab + b²) = 5 : 1? a & b are natural numbers.
- (a)
1 : 2
- (b)
3 : 5
- (c)
5 : 2
- (d)
More than one of the above
Answer: Option C
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Explanation :
⇒
⇒ 2a/b = 5/1
⇒ a/b = 5/2
Hence, option (c).
Workspace:
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