Question

3 darma is edging a tablecloth with lace. the tablecloth is 210 cm by 180 cm. how much lace does she need?

Explanation:

Step1: Identify the shape and formula

The tablecloth is a rectangle. To find the length of lace needed (which is the perimeter of the rectangle), we use the formula for the perimeter of a rectangle: \( P = 2\times(l + w) \), where \( l \) is the length and \( w \) is the width. Here, \( l = 210 \, \text{cm} \) and \( w = 180 \, \text{cm} \).

Step2: Substitute values into the formula

Substitute \( l = 210 \) and \( w = 180 \) into the formula: \( P = 2\times(210 + 180) \). First, calculate the sum inside the parentheses: \( 210 + 180 = 390 \). Then multiply by 2: \( 2\times390 = 780 \).

Answer:

780 cm