Correct Answer - Option 3 : 6.5 ml
Given:
The ratio of coffee and water in 351 ml of combination = 5 ∶ 4
The new combination has coffee and water in ratio = 6 ∶ 5
Concept Used:
Quantity of item = [(Value of antecedent or consequent)/(Sum of antecedent and consequent)] × (Total quantity of combination)
Calculation:
Quantity of coffee = [(5)/(5 + 4)] × 351
⇒ (5/9) × 351
⇒ 195 ml
Quantity of water = [(4)/(5 + 4)] × 351
⇒ (4/9) × 351
⇒ 156 ml
Let x ml water be added
According to question
195 ∶ (156 + x) = 6 ∶ 5
⇒ 195 × 5 = 6 × (156 + x)
⇒ 975 = 936 + 6x
⇒ 975 - 936 = 6x
⇒ 39 = 6x
⇒ 6.5 ml = x
∴ 6.5 ml of water is to be added to get the new ratio 6 ∶ 5.