68. (02-6-15) a ning b ga nisbati 4: 5, b ning s ga nisbati 7: 8 kabi. s ning necha foizini a tashkil qiladi? A) 60 B) 75 C) 70 D) 80 E) 50

\(\frac{a}{b} = \frac{4}{5}\)

\(\frac{b}{c} = \frac{7}{8}\)

\(\frac{a}{c} = \frac{a}{b} \cdot \frac{b}{c} = \frac{4}{5} \cdot \frac{7}{8} = \frac{7}{10} = 0.7\)

В процентах это 0.7 * 100% = 70%.

Ответ: C) 70