1.
If 3 x = 5 y = 4 z, then x : y : z is equal to –
Correct Answer:
4
Description:
LCM OF 3, 5 & 4 = 60; So, (3x/60) = (5y/60) = (4z/60); OR (x/20) = (y/12) / (z/15); Hence, x : y : z = 20 : 12 : 15

2.
If x : y = 4 : 9, and x : z = 2 : 3, then find (x + y) : (x + z).
Correct Answer:
1
Description:
x : y = 4 : 9, and x : z = 2 : 3; OR x : z = 6 : 9 (x + y) : (x + z) = (x + y) / (x + z) = (4+9) / (4 + 6) = 13 / 10 = 13 : 10

3.
If (a + b) : (b + c) : (c + a) = 6 : 7 : 8 and (a + b + c) = 14, then find the value of c.
Correct Answer:
1
Description:
Let k = (a + b)/6 = (b + c) / 7 = (c + a)/8 ; So, (a+b) = 6k; (b+c) = 7k & (c+a) = 8k; Now, a + b + b + c + c + a = 6k + 7k + 8k; 2 x 14 = 21k ; OR k = 28 / 21 = 4 / 3; c = (a+b+c) – (a+b) = 14 – 6k = 14 – 8 = 6

4.
The ratio of number of boys and girls in a school of 720 students is 7 : 5. How many more girls should be admitted to the school, so that the number of girls becomes equal to number of boys?
Correct Answer:
2
Description:
Boys = 420, Girls = 300; Let x girls be admitted, so that the number of girls becomes equal to the number of boys. Then, 300 + x = 400; x = 120

5.
The cost of two books is equal to cost of five pens. If the total cost of 7 books and 4 pens is Rs 1290/, what is the cost of 1 book?
Correct Answer:
4
Description:
Let the cost of a book be Rs B & the cost of a pen be Rs P. 2B = 5P; So, 1B = 5P/2; 7B + 4P = 1290; or, (7*5P/2) + 4P = 1290; P = Rs 60/ ; B = 5*60/2 = Rs 150/
