102
Decimal places: tenths
Textbook: Part 3, lesson 102, pp. 98–100
GoalThe tenths place: changing fractions with denominator 10 into decimals; adding and subtracting decimals (through common fractions).
New words
tenths place · o‘ndan birlar xonasiwhole part · butun qismadding decimals · o‘nli kasrlarni qo‘shishconvert · aylantirish
Explanation
A common fraction with denominator 10 becomes a decimal with one digit after the point: 7/10 = 0.7, 3 4/10 = 3.4, 12/10 = 1 2/10 = 1.2. For now we add and subtract decimals by changing them into common fractions: 4.2 + 1.3 = 4 2/10 + 1 3/10 = 5 5/10 = 5.5. If the fraction parts add to more than 10/10, take the whole out: 2.6 + 5.7 = 7 + 13/10 = 8 3/10 = 8.3.
Worked examples
6.3 + 2.4 = 6 3/10 + 2 4/10 = 8 7/10 = 8.7.
8.2 − 3.9 = 8 2/10 − 3 9/10 = 7 12/10 − 3 9/10 = 4 3/10 = 4.3.
Class activity
“Number path”: a 0 to 3 m tape is stuck on the floor with each metre split into 10. A child stops at 1.4, 2.0 and 2.7 and reads the decimal.
Practice
1
Write 5/10 and 12/10 as decimals.
0.5; 1.2
2
Write 0.3 and 2.8 as common fractions.
3/10; 2 8/10
3
Work out 4.6 + 3.8.
8.4
4
Work out 8.2 − 3.9.
4.3
5
On a ruler each centimetre is split into 10 equal parts. The tip of a pencil reaches the 7th mark after 12 cm. How many centimetres long is the pencil?
12.7