Question

A pile of 10 books is 21 cm. How thick is 2 books in mm​

Answer 1

Answer:

42 mm

Step-by-step explanation:

10 books are 21 cm or 210 mm thick, hence 1 book is 21 mm thick. hence 2 books are 21*2=42 mm thick.

Answer 2

Answer:

Consider the length =x

Book:Length::Book:Length=10:21::2:x

$= \frac{10}{21 } = \frac{2}{x} \\ 10 \times x = 21 \times 2 \\ x = \frac{21 \times 2}{10} = \frac{21}{5} cm = \frac{21}{5} \times 10 = \\ 42mm$