Ratio and Proportion with Explanation

Q15. 100 kg of solution A is mixed with 60 kg of solution B. If solution A has tin and copper in the ratio 1 : 4 and solution B has lead and tin in the ratio 3 : 2, then what is the amount of tin in the new solution?

Answer- Option D

Explanation-

Quantity of tin in solution A =

1 5

x 100

kg = 20 kg

Quantity of tin in solution B =

2 5

x 60

kg = 24 kg

Quantity of tin in the new solution = (20 + 24) kg = 44 kg

Q16. A purse has Rs. 10, Rs. 5, and Rs. 2 coins in the ratio 9 : 5 : 4 amounting to Rs. 1866. Find the number of Rs. 10 coins in the purse?

Answer- Option C

Explanation-

Let the number of Rs. 10, Rs. 5, and Rs. 2 coins be 9x, 5x, and 4x
Then, 10*9x + 5*5x + 2*4x = Rs. 1866
933x = 1866
x = 2
The number of Rs. 10 coins is 9x = 18

Q17. The average age of three friends is 25 years. Their ages are in the proportion 5 : 7 : 3. Find the age of eldest friend?

Answer- Option A

Explanation-

Let their ages be 5x, 7x, and 3x
Sum of their ages = 25*3 = 75 years
Then, 5x + 7x + 3x = 75
15x = 75
x = 5
Age of eldest friend is 7x = 35 years