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51. If Rs. 782 be divided into three parts, proportional to 12 : 23 : 34 then the first part is:

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Solution:
(12:23:34)×126:8:91stpart'sshare=Rs.(623×782)=Rs.6×34=Rs.204
52. The salaries A, B, C are in the ratio 2 : 3 : 5. If the increments of 15%, 10% and 20% are allowed respectively in their salaries, then what will be new ratio of their salaries?

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Solution:
Let,A=2kB=3kandC=5kAsnewsalary=115100of2k=115100×2k=23k10Bsnewsalary=110100of3k=110100×3k=33k10Csnewsalary=120100of5k=120100×5k=6kNewratio=23k10:33k10:6k=23:33:60
53. If 40% of a number is equal to two-third of another number, what is the ratio of first number to the second number?

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Solution:
Let40%ofA=23BThen,40A100=2B32A5=2B3AB=23×52=53A:B=5:3
54. The fourth proportional to 5, 8, 15 is:

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Solution:
Letthefourthproportionalto5,8,15bexThen,5:8:15:x5x=8×15x=8×155=24
55. Two number are in the ratio 3 : 5. If 9 is subtracted from each, the new numbers are in the ratio 12 : 23. The smaller number is:

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Solution:
Letthenumberbe3xand5xThen,3x95x9=122323(3x9)=12(5x9)9x=99x=11Thesmallernumber=3×11=33
56. In a bag, there are coins of 25 p, 10 p and 5 p in the ratio of 1 : 2 : 3. If there is Rs. 30 in all, how many 5 p coins are there?

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Solution:
Let the number of 25 p, 10 p and 5 p coins be x, 2x, 3x respectively
Then, sum of their values
=Rs.(25x100+10×2x100+5×3x100)=Rs.60x10060x100=30x=30×10060=50Hence,thenumberof5pcoins=(3×50)=150
57. What is the ratio in Rs. 2.80 and 40 paise?

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Solution:
Rs. 2.80 = 280 paise
∴ Required ration = 280 : 40
= 7 : 1
58. A person spends Rs. 8100 in buying some tables at Rs. 1200 each and some chairs at Rs. 300 each. The ratio of the number of chairs to that of tables when the maximum possible number of tables is purchased,

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Solution:
Maximum possible number of tables = 6
[∵ 1200 × 6 = 7200]
Number of chairs purchased
 = 81007200300 = 900300 = 3Hence,Required ratio=3:6 = 1:2
59. If x=13y   and y=12z,   then x : y : z is equal to = ?

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Solution:
x=13yand y=12zxy=13and yz=12x:y=1:3y:z=1:2×3(multiply)i.e.y:z=3:6x:y:z=1:3:6
60. If x : y = 3 : 1, then x3 - y3 : x3 + y3 = ?

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Solution:
x:y=3:1xy=31x3y3x3+y3y3(x3y31)y3(x3y3+1)taking y3 common = x3y31x3y3+127127+126281314