1. **State the problem:** We are given a rectangle where the length is three times the width, and the area is 147 cm². We need to find the perimeter. 2. **Define variables:** Let the width be $w$ cm. 3. **Express length:** Length $l = 3w$ cm. 4. **Use the area formula:** Area $A = l \times w$. 5. **Substitute values:** $147 = 3w \times w = 3w^2$. 6. **Solve for $w^2$:** $$ 3w^2 = 147 \\ \cancel{3}w^2 = \cancel{3}49 \\ w^2 = 49 $$ 7. **Find $w$:** $$ w = \sqrt{49} = 7 \text{ cm} $$ 8. **Find length $l$:** $$ l = 3w = 3 \times 7 = 21 \text{ cm} $$ 9. **Find perimeter $P$:** Perimeter of rectangle is $$ P = 2(l + w) = 2(21 + 7) = 2 \times 28 = 56 \text{ cm} $$ **Final answer:** The perimeter is **56 cm**.