Question

By guessing, $105\times 21$ is nearly ____ and by calculating, it is ____.

• A. 2205, 2000
• B. 2000, 2205
• C. 2050, 2000
• D. 2000. 2050

Answer 1

The correct option is B 2000, 2205

$105\times 21$ is nearly $100\times 20.$
$100\times 20=2000$
$\therefore$ On guessing, $105\times 21$ is nearly $2000$.

$105\times 21$ can be calculated using boxes.

$105\times 21=2000+100+100+5=2205$
$\therefore$ On calculating, $105\times 21=2205$.