Multiplying and dividing weights

In your book, Maths Mela (Chapter 8), a farmer has 4 sacks of potatoes, and each weighs 10 kg 500 g. What is the total weight? Multiply the kilograms and the grams separately: 4 × 10 kg = 40 kg and 4 × 500 g = 2,000 g = 2 kg. Together, 40 kg + 2 kg = 42 kg. Or change to grams: 4 × 10,500 g = 42,000 g = 42 kg.

A box of nuts weighing 4 kg 800 g is shared equally into 4 smaller boxes. Divide each part: 4 kg ÷ 4 = 1 kg and 800 g ÷ 4 = 200 g. So each small box holds 1 kg 200 g, which is 1,200 g. In grams: 4,800 g ÷ 4 = 1,200 g.

Cost grows in step with weight. Rice costs ₹60 for 1 kg. For 12 kg 500 g: 12 kg cost 12 × ₹60 = ₹720, and 500 g is half a kilogram, so it costs half of ₹60, which is ₹30. In all, ₹720 + ₹30 = ₹750. If 5 kg of tomatoes cost ₹73, then 10 kg, which is double, cost double: ₹146. If 4 people need 500 g of rice, 8 people need double: 1,000 g.

Nitesh, the scrap dealer, pays ₹8 for every 1 kg of old newspaper, so 16 kg cost him 16 × ₹8 = ₹128. He pays ₹200 for every 10 kg of iron, so 20 kg cost ₹400.

In the story of the King's Weight, a king gives away wheat equal to 10 times his weight on his birthday. This year he gives 800 kg. So his weight is 800 kg ÷ 10 = 80 kg. Last year he gave 780 kg, so he weighed 78 kg then. He gained 80 kg − 78 kg = 2 kg in a year.