Carcass wrote:

Chelsea has 5 roses and 2 jasmines. A bouquet of 3 flowers is to be formed. In how many ways can it be formed if at least one jasmine must be in the bouquet?

(A) 5

(B) 20

(C) 25

(D) 35

(E) 40

Here,

Let us consider the possibilities::

CASE I 1 rose and 2 jasmines which can be arranged in = 5C1 * 2C2 = 20

CASE II2 roses and 1 jasmines which can be arranged in = 5C2 * 2C1 = 5

Therefore the total no. of possibilities = 20 + 5 = 25

I think you got the calculations mixed up. 5C2 * 2C1 = 20 etc.