suppose that 12 inches of wire costs 36 cents.At the same rate, how many inches of wire can be bought for 21 cents?
suppose that 12 inches of wire costs 36 cents.At the same rate, how many inches of wire can be bought for 21 cents?
\(\small{ \begin{array}{rcll} \dfrac{ 12\ \text{inches} } { 36\ \text{cents} } \cdot 21\ \text{cents} &=& \dfrac{12}{36}\cdot 21 \ \text{inches} \\\\ &=& \dfrac{1}{3}\cdot 21 \ \text{inches} \\\\ &=& \dfrac{21}{3} \ \text{inches} \\\\ &=& 7 \ \text{inches of wire} \\\\ \end{array} } \)
12 = x
36 = 21
Cross multiply
12*21=36x
252=36x
Divide 36 on both sides
7=x
7 inches of wire
suppose that 12 inches of wire costs 36 cents.At the same rate, how many inches of wire can be bought for 21 cents?
\(\small{ \begin{array}{rcll} \dfrac{ 12\ \text{inches} } { 36\ \text{cents} } \cdot 21\ \text{cents} &=& \dfrac{12}{36}\cdot 21 \ \text{inches} \\\\ &=& \dfrac{1}{3}\cdot 21 \ \text{inches} \\\\ &=& \dfrac{21}{3} \ \text{inches} \\\\ &=& 7 \ \text{inches of wire} \\\\ \end{array} } \)