Question

19．計(jì)算：$\frac{1}{4}$×39+$\frac{3}{4}$×27．

Answer 1

分析 把$\frac{1}{4}$×39+$\frac{3}{4}$×27改寫(xiě)成$\frac{1}{4}$×39+$\frac{1}{4}$×3×27，即$\frac{1}{4}$×$39+\frac{1}{4}$×81，然后再利用乘法分配律的逆運(yùn)算進(jìn)行計(jì)算．

解答 解：$\frac{1}{4}$×39+$\frac{3}{4}$×27
=$\frac{1}{4}$×$39+\frac{1}{4}$×3×27
=$\frac{1}{4}$×$39+\frac{1}{4}$×81
=$\frac{1}{4}$×（39+81）
=$\frac{1}{4}$×120
=30

點(diǎn)評(píng) 本題關(guān)鍵是要把$\frac{1}{4}$×39+$\frac{3}{4}$×27改寫(xiě)成$\frac{1}{4}$×$39+\frac{1}{4}$×81來(lái)進(jìn)行解答．