Printable primary math worksheet for math grades 1 to 6 based on ... - Free Printable

We are given a worksheet with fraction addition problems where one numerator is missing (shown as a blank box). All fractions in each equation have the same denominator, so we can solve by focusing on the numerators only.

Recall:
If $\frac{a}{d} + \frac{b}{d} = \frac{c}{d}$, then $a + b = c$.
So to find the missing numerator, subtract the known numerator from the result’s numerator.

Let’s go row by row and solve each equation:

---

Row 1:
1. $\frac{1}{6} + \frac{?}{6} = \frac{2}{3}$
First, convert $\frac{2}{3}$ to sixths: $\frac{2}{3} = \frac{4}{6}$.
So: $1 + ? = 4$ → $? = 3$

2. $\frac{1}{10} + \frac{?}{10} = \frac{2}{5}$
Convert $\frac{2}{5} = \frac{4}{10}$.
So: $1 + ? = 4$ → $? = 3$

---

Row 2:
3. $\frac{1}{4} + \frac{?}{4} = \frac{1}{2}$
$\frac{1}{2} = \frac{2}{4}$ → $1 + ? = 2$ → $? = 1$

4. $\frac{1}{12} + \frac{?}{12} = \frac{1}{3}$
$\frac{1}{3} = \frac{4}{12}$ → $1 + ? = 4$ → $? = 3$

5. $\frac{6}{18} + \frac{?}{18} = \frac{1}{2}$
$\frac{1}{2} = \frac{9}{18}$ → $6 + ? = 9$ → $? = 3$

---

Row 3:
6. $\frac{1}{10} + \frac{?}{10} = \frac{1}{2}$
$\frac{1}{2} = \frac{5}{10}$ → $1 + ? = 5$ → $? = 4$

7. $\frac{1}{8} + \frac{?}{8} = \frac{1}{2}$
$\frac{1}{2} = \frac{4}{8}$ → $1 + ? = 4$ → $? = 3$

8. $\frac{2}{6} + \frac{?}{6} = \frac{2}{3}$
$\frac{2}{3} = \frac{4}{6}$ → $2 + ? = 4$ → $? = 2$

---

Row 4:
9. $\frac{1}{6} + \frac{?}{6} = \frac{1}{3}$
$\frac{1}{3} = \frac{2}{6}$ → $1 + ? = 2$ → $? = 1$

10. $\frac{2}{15} + \frac{?}{15} = \frac{1}{3}$
$\frac{1}{3} = \frac{5}{15}$ → $2 + ? = 5$ → $? = 3$

11. $\frac{5}{12} + \frac{?}{12} = \frac{2}{3}$
$\frac{2}{3} = \frac{8}{12}$ → $5 + ? = 8$ → $? = 3$

---

Row 5:
12. $\frac{5}{10} + \frac{?}{10} = \frac{4}{5}$
$\frac{4}{5} = \frac{8}{10}$ → $5 + ? = 8$ → $? = 3$

13. $\frac{3}{8} + \frac{?}{8} = \frac{3}{4}$
$\frac{3}{4} = \frac{6}{8}$ → $3 + ? = 6$ → $? = 3$

14. $\frac{2}{20} + \frac{?}{20} = \frac{1}{4}$
$\frac{1}{4} = \frac{5}{20}$ → $2 + ? = 5$ → $? = 3$

---

Row 6:
15. $\frac{9}{20} + \frac{?}{20} = \frac{3}{4}$
$\frac{3}{4} = \frac{15}{20}$ → $9 + ? = 15$ → $? = 6$

16. $\frac{1}{8} + \frac{?}{8} = \frac{1}{4}$
$\frac{1}{4} = \frac{2}{8}$ → $1 + ? = 2$ → $? = 1$

17. $\frac{1}{16} + \frac{?}{16} = \frac{1}{4}$
$\frac{1}{4} = \frac{4}{16}$ → $1 + ? = 4$ → $? = 3$

---

Row 7:
18. $\frac{2}{9} + \frac{?}{9} = \frac{1}{3}$
$\frac{1}{3} = \frac{3}{9}$ → $2 + ? = 3$ → $? = 1$

19. $\frac{7}{25} + \frac{?}{25} = \frac{3}{5}$
$\frac{3}{5} = \frac{15}{25}$ → $7 + ? = 15$ → $? = 8$

20. $\frac{3}{9} + \frac{?}{9} = \frac{2}{3}$
$\frac{2}{3} = \frac{6}{9}$ → $3 + ? = 6$ → $? = 3$

---

Now let’s list all missing numerators in order (left to right, top to bottom):

1. 3
2. 3
3. 1
4. 3
5. 3
6. 4
7. 3
8. 2
9. 1
10. 3
11. 3
12. 3
13. 3
14. 3
15. 6
16. 1
17. 3
18. 1
19. 8
20. 3

Let me double-check a few tricky ones:

- #15: $\frac{9}{20} + \frac{6}{20} = \frac{15}{20} = \frac{3}{4}$ ✔
- #19: $\frac{7}{25} + \frac{8}{25} = \frac{15}{25} = \frac{3}{5}$ ✔
- #20: $\frac{3}{9} + \frac{3}{9} = \frac{6}{9} = \frac{2}{3}$ ✔
- #14: $\frac{2}{20} + \frac{3}{20} = \frac{5}{20} = \frac{1}{4}$ ✔

All correct.

Final Answer:
3, 3, 1, 3, 3, 4, 3, 2, 1, 3, 3, 3, 3, 3, 6, 1, 3, 1, 8, 3