Question

Вопрос: Решите пропорцию:


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Answer 1

$======== 1 ======== \\ x:8 = 28:7\\ 7 \cdot x = 28 \cdot 8\\ 7x = 224 |:7\\ x=32\\ ======== 2 ======== \\ 5:x=25:10\\ 25 \cdot x = 5 \cdot 10\\ 2x=50 |:2\\ x=25\\ ======== 3 ======== \\ 100:4 = x:3\\ 4 \cdot x = 3\cdot100\\ 4x=300 |:4\\ x=75\\ ======== 4 ======== \\ 36:3=480:x\\ 36\cdot x = 3 \cdot 480\\ 36x = 1440 |:36\\ x=40\\ ======== 5 ======== \\ x:2.5=18:6\\ 6 \cdot x = 18 \cdot 2.5\\ 6x = 45 |:6\\ x=7.5$
$======== 6 ======== \\ \frac{1}{5} : x = 4:2\\ 4 \cdot x = \frac{1}{5} \cdot 2\\ 4x= \frac{2}{5} |:4\\ x= \frac{1}{10} \\ ======== 7 ======== \\ 10:2.5=x:32\\ 2.5 \cdot x = 10 \cdot 32\\ 2.5x = 320 |:2.5\\ x=128\\ ======== 8 ======== \\ 16:0.32 = 10:x\\ 16 \cdot x = 10 \cdot 0.32\\ 16x = 3.2 |:16\\ x=0.2\\ ======== 9 ======== \\ 3 \frac{1}{2} :x=2.8:0.2\\ \frac{7}{2} :x=2.8:0.2\\ 3.5 :x=2.8:0.2\\ 2.8 \cdot x = 0.2 \cdot 3.5\\ 2.8x = 0.7 |:2.8\\ x=0.25$