JAMB 2021 Mathematics · Question 30

Three children shared a basket of mangoes in such a way that the first child took 1/4 of the mangoes and the…

Question

Three children shared a basket of mangoes in such a way that the first child took 14\frac{1}{4} of the mangoes and the second 34\frac{3}{4} of the remainder. What fraction of the mangoes did the third child take?

  1. A.316\frac{3}{16}
  2. B.716\frac{7}{16}
  3. C.916\frac{9}{16}
  4. D.1316\frac{13}{16}

Answer: A. 316\frac{3}{16}

Explanation written with AI and checked against the answer key

Analysis

To solve this problem, we need to determine the portion of the basket left after each child takes their share. We start with a whole basket, represented by the fraction 11.

Concept

When dealing with "remainders" in fractions, we subtract the portion taken from the total to find what is left. We then apply the next fraction to that specific remainder.

Step-by-Step Solution

Step 1: Find the remainder after the first child. The first child took 14\frac{1}{4} of the mangoes.

Remainder1=1−14=34\text{Remainder}_1 = 1 - \frac{1}{4} = \frac{3}{4}

Step 2: Find the share of the second child. The second child took 34\frac{3}{4} of the remainder.

Second child’s share=34×34=916\text{Second child's share} = \frac{3}{4} \times \frac{3}{4} = \frac{9}{16}

Step 3: Find the share of the third child. The third child gets whatever is left after the first and second children have taken their portions.

Total taken by first and second=14+916\text{Total taken by first and second} = \frac{1}{4} + \frac{9}{16}

To add these, find a common denominator (which is 16):

416+916=1316\frac{4}{16} + \frac{9}{16} = \frac{13}{16}

Now, subtract this total from the whole basket (11):

Third child’s share=1−1316\text{Third child's share} = 1 - \frac{13}{16}
Third child’s share=1616−1316=316\text{Third child's share} = \frac{16}{16} - \frac{13}{16} = \frac{3}{16}
Conclusion

The third child took 316\frac{3}{16} of the mangoes. This matches option A.

Exam Tip

Whenever you see the phrase "of the remainder," always calculate the remaining fraction first before multiplying. A common mistake is to multiply the second fraction by the original total instead of the remainder. Always check that your final fractions add up to 11 (416+916+316=1616=1\frac{4}{16} + \frac{9}{16} + \frac{3}{16} = \frac{16}{16} = 1).

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