76
Finding a part of a number
Textbook: Part 3, lesson 76, pp. 16–18
GoalFinding a part of a number: divide by the denominator, then multiply by the numerator.
New words
part of a number · sonning qismidivide by the denominator · maxrajga bo‘lishmultiply by the numerator · suratga ko‘paytirishthe remaining part · qolgan qism
Explanation
To find 1/n of a number, divide it by n. To find m/n of a number, first divide by n (this gives one share) and then multiply the result by m. For example 3/4 of 24: 24 : 4 = 6, 6 × 3 = 18. If we subtract the part from the whole, we get the remaining part.
Worked examples
2/5 of 35 kg of rice: 35 : 5 = 7, 7 × 2 = 14 kg.
A plate holds 42 cherries and 1/6 were eaten: 42 : 6 = 7 eaten, 42 − 7 = 35 left.
Class activity
“Shop game”: pupils split a set of 36 items (buttons, pencils) into 1/2, 1/3, 1/4, 2/3 and 3/4 and check by counting how many items each part has.
Practice
1
Find 1/8 of 56.
7
2
Find 2/5 of 45.
18
3
A sack held 72 kg of potatoes and 5/8 of it was sold. How many kilograms were sold?
45
4
In the problem above, how many kilograms of potatoes are left?
27
5
A book costs 45 000 sum. 2/5 of the price was paid in advance. How many sum was paid?
18000