We are required to choose the fraction that has not been reduced to simplest form
The fraction that has not been reduced to simplest form is 19/38 and 10/18
1. 21 / 34 is in its simplest form
factors of 21 = 1, 7 and 21
factors of 34 = 1, 2, 17 and 34
No common factor of 21 and 34 except 1
2. 15/16
factors of 15 = 1, 3, 5, 15
Factors of 16 = 1, 2, 4, 8 and 16
No common factor of 15 and 16 except 1
3. 19/38
factors of 19 = 1, 19
factors of 38 = 1, 2, 19 and 38
divide both numerator and denominator by 19
So,
19 / 38 = 1/2
4. 10/18
factors of 10 = 1, 2, 5 and 10
factors of 18 = 1, 2, 3, 6, 9 and 18
So,
10/18
divide both numerator and denominator by 2
= 5/9
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