Explanation:
take the area of the big circle which goes by the formula πR² which is 22/7×42×42 =5544cm²
take the radius of the big circle as the diameter of the big circle .divide it by 2 to get 21
then take the small circle by πr² which is 22/7× 21×21 = 1386cm²
. substract 5544-1386 to get 4158cm²