A quarter kilogram of potatoes costs 60 paise. At the same rate, how many paise will 200 grams of potatoes cost?

Introduction / Context:
This is another direct proportion question using the unitary method, now with potatoes instead of carrots. It checks whether you can convert between kilograms and grams, and then correctly scale the cost according to the new quantity. These small numerical questions are typical in entry level aptitude tests.

Given Data / Assumptions:

• Cost of one quarter kilogram of potatoes (250 grams) is 60 paise.
• The cost per gram of potatoes is constant.
• We want the cost of 200 grams of potatoes.

Concept / Approach:
The cost of a given weight is directly proportional to that weight when the price per gram is constant. We either compute the cost per gram and multiply by 200 grams, or use a ratio to relate the costs for 250 grams and 200 grams. Both are straightforward applications of the unitary method.

Step-by-Step Solution:
Step 1: One quarter kilogram equals 250 grams.Step 2: Cost for 250 grams is 60 paise.Step 3: Cost per gram = 60 / 250 paise.Step 4: Cost for 200 grams = (60 / 250) * 200 paise.Step 5: Simplify: 60 * 200 / 250 = 60 * (4 / 5) = 48 paise.

Verification / Alternative check:
Observe that 200 grams is four fifths of 250 grams. Therefore, cost for 200 grams must be four fifths of 60 paise. Compute 60 * 4 / 5 to obtain 48 paise directly, which matches the detailed calculation. This ratio based reasoning gives a quick mental check.

Why Other Options Are Wrong:
40 paise would correspond to a rate lower than given by the original data. 54 paise and 60 paise are too high for 200 grams compared to 250 grams, since cost must decrease in proportion. 72 paise is higher than the cost of the larger quantity, which is impossible without a higher rate per gram.

Common Pitfalls:

• Using 200 as denominator and 250 as numerator in the ratio, effectively inverting the proportion.
• Incorrectly converting quarter kilogram, for example, taking it as 200 grams instead of 250 grams.
• Rounding prematurely instead of working with exact fractions until the end.

Final Answer:
The cost of 200 grams of potatoes is 48 paise.