Question

Using each of the digits 2 through 5 only

Answer 1

Answer:

52, 43

Step-by-step explanation:

the first instinct might be to make the first number as big as possible : 54

that leaves for the second number 2 and 3, and the largest combination here is 32 (larger than 23).

54×32 = 1728

but, the area of a rectangle (and that is what we are calculating here) is the larger, the closer the lengths of its side are.

so, a bigger difference between length and width creates a smaller area, than a smaller difference between length and width for similar lengths.

so, what if we sacrifice just a little bit of the length, and make it 53 ? that opens up 4 for the second number, giving us 42 as width. they are much closer to each other with still very similar length.

53×42 = 2226

you see ? much bigger.

let's experiment further and pick 52 as length.

that gives us 43 as width.

52×43 = 2236

and again a little bit closer and with bigger result.

you see, in the previous case we "added" comparably to this last case a 42 (53×42 instead of 52×42), and in the last case we added a 52 (52×43 instead of 52×42) creating the difference of 10.

but of course, this only works, if we don't decrease the length too much.

Answer 2

Answer:

Using each of the digits 2 through 5 only once, write 2 two-digit whole numbers whose product is as large as possible.