94
Subtracting from one
Textbook: Part 3, lesson 94, pp. 72–74
GoalSubtracting a fraction from 1: writing 1 as a fraction with the same denominator.
New words
subtract from one · birdan ayirishthe rest · qolgan qismsubtrahend · ayriluvchiwhole · butun
Explanation
To subtract a fraction from 1, write 1 as a fraction whose denominator equals the denominator of the fraction being subtracted: 1 = 7/7. Then subtract the numerators: 1 − 3/7 = 7/7 − 3/7 = 4/7. In such problems, taking a part from the whole leaves the rest.
Worked examples
1 − 5/12 = 12/12 − 5/12 = 7/12.
2/9 of a flatbread was eaten. What is left: 1 − 2/9 = 9/9 − 2/9 = 7/9.
Class activity
“Make the whole”: a paper square is split into 10 equal parts. Children colour some parts and write the uncoloured part as 1 minus the coloured fraction.
Practice
1
Work out 1 − 3/7.
4/7
2
Work out 1 − 5/12.
7/12
3
Work out 1 − 9/10.
1/10
4
A jug was full and 4/15 of it was poured out. What part of the jug is left?
11/15
5
Solve the equation: x + 3/11 = 1.
8/11