standard deviation

[ahlashi]

a set of 16 real no.is multiplied by a positive real no.
after multiplication the variace of the resulting set of  no. is found to be 6.25 times the variance of the set of numbers of the set b4 multipliation
what is the no. which was used to multiply all the observations

pls if any1 could explain

[Amit Goyal]

V(cX) = c^2 V(X)

Find c given c^2 = 6.25.