Yvon has 4 different notebooks and 5 different pens. He must bring exactly one notebook and exactly one pen to his class. How many different possible combinations of notebooks and pens could he bring?
, 2020
Pick one
Solution
Since the third and fourth numbers in the list are consecutive and add to 11, then the third number in the list is 5 and the fourth is 6.
The fifth number in the list is 7, and so the sixth number in the list is 8.
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