The bright graduate

Young Smitherly, who was about to graduate at the head of his class at Upcoming University, was in the pleasant position of having his choice of two very attractive offers both at $5000 a year. Unable to make up his mind between them immediately, he wrote the two companies and asked what his chances were for raises over the next five years.
Company A replied to the effect that it would guarantee a raise of $300 every six month for the next five years. Company B said it would guarantee a raise of $1200 every twelve months for the next five years.
To the astonishment of his father, Smitherly accepted Company A's offer. Why?

Solution :
During each year Smitherly would receive the following from the two companies :
Year first
A>2500+2800=5300
B>5000
Year second
A>3100+3400=6500
B>6200
Year third
A>3700+4000=7700
B>7400
Year fourth
A>4300+4600=8900
B>8600
Year fifth
A>4900+5200=10100
B>9800
in the other words, Company A's offer is $300 a year better than Company B's.
This looks like paradox but it isn't. A raise in semiannual pay of $300 is the same as a raise of $600 in annual pay. Since Company A was offering two such raises, or $1200 a year, it was equivalent to Company A's offer except that, as a result of the semiannual feature, each year he would get $300 of this $1200 raise six months earlier. -QED-