Radius of two circular wheels shown are 21 cm and 12 cm, respectively. The wheels are connected as gear, so they rotate with each other. If the second wheel makes 840 revolutions, find the number of revolutions made by the first wheel.
Find the compound interest of ^@ €50000 ^@ after ^@ 2 ^@ years, compounded annually. The rate of interest is ^@ 18 \% ^@ per annum during the first year and ^@ 17 \% ^@ per annum during the second year.