To form a composite  16μF, 1000V capacitor from a supply of identical capacitors marked  8μF, 250V, we require a minimum number of capacitors

Suppose C = 8 μF , C' = 16μF and V = 250 V, V' = 1000V  Suppose m rows of given capacitors are connected in parallel and each row contains n capacitors then potential difference across each capacitor  V=V'n and equivalent capacitance of network C'=mCn on putting the values we get n = 4 and m = 8∴Total capacitors = n × m = 4 ×8 = 32