Question

300 gms of salt solution has 40% salt in it. How much salt should be added to make it 50% in the solution?

• A. 40 gms
• B. 60 gms
• C. 70 gms
• D. 80 gms

Hint:

The non-salt part of the solution stays the same when you add pure salt, use that to find the new total weight.

Answer 1

The Correct Option is B

Step 1: Find the salt already present.
The solution weighs 300 gm and has 40% salt, so salt present = 40% of 300 = 120 gm. The non-salt part = 300 - 120 = 180 gm.

Step 2: Add unknown salt \(x\).
Adding pure salt keeps the 180 gm non-salt part unchanged, but total salt becomes \(120 + x\) and total solution becomes \(300 + x\).

Step 3: Set up the 50% condition. \[ \frac{120 + x}{300 + x} = \frac{1}{2} \]

Step 4: Solve for \(x\).
Cross multiply: \[ 2(120 + x) = 300 + x \] \[ 240 + 2x = 300 + x \] \[ x = 60 \]

Step 5: Rule out the other options.
Option A (40 gm) gives a ratio below 50%, and options C (70 gm) and D (80 gm) push the ratio above 50%. Only 60 gm lands exactly on 50%.

Final Answer:
60 gm of salt must be added. \[ \boxed{60 \text{ gm}} \]