How many 3-digit even numbers are there that begin with either 5 or 6?

100 numbers

Step-by-step explanation:

There are 100 numbers with 5 as the hundreds digit. (500-599)

There are 100 numbers with 6 as the hundreds digit. (600-699)

There are 50 even numbers with 5 as the hundreds digit.

(500, 502, 504, ... , 598)

There are 50 even numbers with 6 as the hundreds digit.

(600, 602, 604, ... , 698)

50+50=100 numbers

1/3 + 1/3 ≠ 2/6 because 1/3 alone = 2/6  

step by step explanation:

1/3 + 1/3 = 2/3       2/3=4/6