Okay, this will be simple.
Notice that 2 1/2 is a mixed number. This needs to be changed to an IMPROPER FRACTION.
To do this, multiply the denominator by the whole number
2 x 2 = 4
Add numerator and keep denominator the same.
5/2.
Okay, so 5/2 x 1/10.
When multiplying fractions, no common denominator is needed. Just multiply the numerators and denominators.
5 x 1 = 5
2 x 10 = 20.
5/20 which reduces to 1/4. (5 is the GCF of 5 and 20, 5 divided by 5 = 1 and 20 divided by 5 = 4)
5/20 or 1/4 is your answer. (they mean the same thing)