Ratio and Proportion online activity for Grade 5 - Free Printable

Let's solve each of these proportion problems using cross multiplication. The general rule for cross multiplication in a proportion:

If
$$
\frac{a}{b} = \frac{c}{d}
$$
then
$$
a \cdot d = b \cdot c
$$

We’ll apply this to each problem.

---

1.

$$
\frac{X}{6} = \frac{15}{18}
$$

Cross multiply:
$$
X \cdot 18 = 6 \cdot 15
$$
$$
18X = 90
$$
$$
X = \frac{90}{18} = 5
$$

✔ X = 5

---

2.

$$
\frac{X}{3} = \frac{16}{24}
$$

Cross multiply:
$$
X \cdot 24 = 3 \cdot 16
$$
$$
24X = 48
$$
$$
X = \frac{48}{24} = 2
$$

✔ X = 2

---

3.

$$
\frac{3}{5} = \frac{X}{15}
$$

Cross multiply:
$$
3 \cdot 15 = 5 \cdot X
$$
$$
45 = 5X
$$
$$
X = \frac{45}{5} = 9
$$

✔ X = 9

---

4.

$$
\frac{X}{6} = \frac{2}{12}
$$

Cross multiply:
$$
X \cdot 12 = 6 \cdot 2
$$
$$
12X = 12
$$
$$
X = \frac{12}{12} = 1
$$

✔ X = 1

---

5.

$$
\frac{X}{5} = \frac{16}{20}
$$

Cross multiply:
$$
X \cdot 20 = 5 \cdot 16
$$
$$
20X = 80
$$
$$
X = \frac{80}{20} = 4
$$

✔ X = 4

---

6.

$$
\frac{1}{2} = \frac{X}{8}
$$

Cross multiply:
$$
1 \cdot 8 = 2 \cdot X
$$
$$
8 = 2X
$$
$$
X = \frac{8}{2} = 4
$$

✔ X = 4

---

7.

$$
\frac{X}{8} = \frac{10}{16}
$$

Cross multiply:
$$
X \cdot 16 = 8 \cdot 10
$$
$$
16X = 80
$$
$$
X = \frac{80}{16} = 5
$$

✔ X = 5

---

8.

$$
\frac{X}{2} = \frac{4}{8}
$$

Cross multiply:
$$
X \cdot 8 = 2 \cdot 4
$$
$$
8X = 8
$$
$$
X = \frac{8}{8} = 1
$$

✔ X = 1

---

9.

$$
\frac{X}{4} = \frac{9}{12}
$$

Cross multiply:
$$
X \cdot 12 = 4 \cdot 9
$$
$$
12X = 36
$$
$$
X = \frac{36}{12} = 3
$$

✔ X = 3

---

10.

$$
\frac{1}{3} = \frac{3}{X}
$$

Cross multiply:
$$
1 \cdot X = 3 \cdot 3
$$
$$
X = 9
$$

✔ X = 9

---

✔ Final Answers:

1. X = 5
2. X = 2
3. X = 9
4. X = 1
5. X = 4
6. X = 4
7. X = 5
8. X = 1
9. X = 3
10. X = 9

---

Let me know if you'd like a printed version or explanation with visuals!