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

Suppose C = 8μF, 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 

 and equivalent capacitance of network 

  on putting the values we get n = 4 and m = 8

 Total capacitors = n x m = 4 x 8 = 32

Short Trick : For such type of problems number of capacitors