1. From each of the following groups of numbers, take one number, multiply them, then the sum of all such products is $\qquad$ .

First group: $\frac{3}{4}, 0.15$; Second group: $4, \frac{2}{3}$; Third group: $\frac{3}{5}, 1.2$
Reference answer:
1. Solution: Let the total sum be $S$, then
$$
\begin{array}{l}
\frac{3}{4} \times 4 \times \frac{3}{5}+\frac{3}{4} \times 4 \times 1.2+\frac{3}{4} \times \frac{2}{3} \times \frac{3}{5}+\frac{3}{4} \times \frac{2}{3} \times 1.2+0.15 \times 4 \times \frac{3}{5}+0.15 \times 4 \times 1.2+0.15 \times \frac{2}{3} \times \frac{3}{5}+0.15 \times \frac{2}{3} \times 1.2 \\
=(0.75+0.15) \times\left(4 \times \frac{3}{5}+4 \times 1.2+\frac{2}{3} \times \frac{3}{5}+\frac{2}{3} \times 1.2\right) \\
=0.9 \times(2.4+4.8+0.4+0.8) \\
=0.9 \times 8.4=7.56
\end{array}
$$