681. A:B=2:3, B:C=3:4, A:D=4:5. Find C:D.
A. 2:5
B. 4:5
C. 6:5
D. 8:5

Explanation:
A:C=(A:B)*(B:C) =(2/3)*(3/4)= 1/2 C:D=(C:A)*(A:D) =(2)*(4/5) = 8:5

682. Find the fourth proportion to 3, 7 and 9.
A. 63
B. 31
C. 21
D. 27

Explanation:
3:7::9:x 3x=7*9=63 x=21

683. If 40% of a number is equal to two-third of another number, what is the ratio of first number to the second number ?
A. 2 : 5
B. 3 : 7
C. 5 : 3
D. 7 : 3

684. Seats for Mathematics, Physics and Biology in a school are in the ratio 5 : 7 : 8. There is a proposal to increase these seats by 40%, 50% and 75% respectively. What will be the ratio of increased seats ?
A. 2 : 3 : 4
B. 6 : 7 : 8
C. 6 : 8 : 9
D. None of these

Explanation:
5:7:8 = 50:70:80
50*140/100=70 ; 70*150/100=105 ; 80*175/100=140
70: 105: 140 or
14: 21: 28 or
2: 3: 4

685. 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?
A. 50
B. 100
C. 150
D. 200

686. Two numbers 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 :________?
A. 27
B. 33
C. 49
D. 55

687. Two numbers are respectively 20% and 50% more than a third number. The ratio of the two numbers is :__________?
A. 2 : 5
B. 3 : 5
C. 4 : 5
D. 6 : 7

Explanation:
Let the third number be x.
Then, first number = 120% of x = 120x/100 = 6x/5 second numbet = 150% of x = 150x/100 = 3x/2 Ratio of first two numbers = 6x/5 : 3x/2 =12x : 15x = 4 : 5.

688. A surn of money is to be distributed among A, B, C, D in the proportion of 5 : 2 : 4 : 3. If C gets Rs. 1000 more than D, what is B’s share ?
A. Rs. 500
B. Rs. 1500
C. Rs. 2000
D. None of these

689. The ratio of the number of boys and girls in a college is 7 : 8. If the percentage increase in the number of boys and girls be 20% and 10% respectively, what will be the new ratio ?
A. 8 : 9
B. 17 : 18
C. 21 : 22
D. Cannot be determined

Explanation:
Originally, let the number of boys and girls in the college be 7x and 8x respectively. Their increased number is (120% of 7x) and (110% of 8x), i . e . ( 120/100 X 7x ) and ( 110/100 X 8x ) i . e . 42x/5 and 44x/5 Required ratio = 42x/5 : 44x/5 = 21 : 22

690. The sum of three numbers is 98. If the ratio of the first to the second is 2 : 3 and that of the second to the third is 5 : 8, then the second number is :__________?
A. 20
B. 30
C. 48
D. 58

Explanation:
Let the three parts be A, B, C Then,
A : B = 2 : 3 and B : C = 5 : 8 (5 X 3/5 ) : (8 X 3/5 ) = 3 : 24/5
A:B:C= 2 : 3 : 24/5 10:15:24
B = (98 X 15/49 ) = 30.

NOTE
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