## Elementary Technical Mathematics

1$\frac{1}{4}$ heads
Total number of heads of lettuce = 5$\frac{1}{2}$ Heads of lettuce used for sandwiches = 1$\frac{1}{2}$ Heads of lettuce used for salads = 2$\frac{3}{4}$ Remaining heads of lettuce = 5$\frac{1}{2}$ - 1$\frac{1}{2}$ - 2$\frac{3}{4}$ =$\frac{11}{2}$ - $\frac{3}{2}$ -$\frac{11}{4}$ =$\frac{8}{2}$ - $\frac{11}{4}$ = $\frac{8}{2}\times$ $\frac{2}{2}$ - $\frac{11}{4}$ =$\frac{16}{4}$ - $\frac{11}{4}$ =$\frac{5}{4}$ =1$\frac{1}{4}$ heads