NCERT Solutions for Class 7th Maths Chapter 5 Know Your Onions! — Math Talk

Book page 104 Updated on2026-09-19

Q1.
Find the average price of onions at Yahapur and Wahapur.
Answer

Yahapur ≈ ₹38.17 per kg; Wahapur = ₹37.50 per kg.

Yahapur: 25 + 24 + 26 + 28 + 30 + 35 + 39 + 43 + 49 + 56 + 59 + 44
= 49 + 26 + 28 + 30 + 35 + 39 + 43 + 49 + 56 + 59 + 44
= 458
Average = 458 ÷ 12 = ₹38.17 (to two decimal places)

Wahapur: 19 + 17 + 23 + 30 + 38 + 35 + 42 + 39 + 53 + 60 + 52 + 42
= 450
Average = 450 ÷ 12 = ₹37.50
Why it happens: both towns have 12 months of data, so here the totals and the averages point the same way. The gap is tiny — 67 paise per kilogram over a whole year. On the strength of the averages alone you should say the two towns are nearly the same, with Yahapur very slightly dearer.
Tip: 458 ÷ 12 = 38 remainder 2, so the answer is 38 and 2/12 = 38.1666… ≈ ₹38.17. Never round to "about ₹38" and then claim Yahapur is dearer — after rounding, the two are equal.
Q2.
What else do you wonder about?
Answer

This is an open question — good data always raises more questions than it answers. Here are questions that this particular table really can spark, in the spirit of the ones printed in the book.

  • Both towns are cheapest in February and dearest in October–November. Is that because the new crop arrives in winter and the old stock runs out before it?
  • Yahapur's prices climb steadily month after month; Wahapur's jump about. Does Wahapur have fewer shops, or does it get its onions from further away?
  • In April and May, Wahapur is suddenly dearer than Yahapur by ₹2 and ₹8. Was there a transport problem, or a local festival?
  • What happens to a family's monthly budget when the price goes from ₹17 to ₹60 — more than three times — inside one year?
  • Does the farmer who grew the onions receive three times as much in October as in February, or does the extra money stay with traders?
  • Would potatoes, tomatoes or dal show the same shape over the year?
Why it happens: a single statement like "onions cost ₹35 a kilo" invites no further thought. A table of twelve varying values does, because every rise and dip asks to be explained. Curiosity is the first step of statistics, not the last.
Tip: pick one of your questions and decide what data you would need to answer it. That turns a wondering into a statistical question.
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