Was wondering if you could help please with a riddle question for a math project to be displayed for children to quandary-

Distribute the numbers 1 through 9 on the lines below so that two equations are true.

_ _ x _ = _ _

_ x _ = _ _

Use each digit only once-

thanking you in advance-
Sincerely,
Bonnie

 


Hi Bonnie,

I can get you started by asking "Where do you put the 5?"

If the 5 is here

_ _ 5 = _ _

then the last digit on the right is either a 5 or a 0. A 0 is not allowed and neither is a second 5.

If the 5 is here

5 _ = _ _

or

_ 5 = _ _

then again the last digit on the right is either a 0 or a 5, both of which you can't have.

If the 5 is here

5_ _ = _ _

then the number on the right of the equal sign would be a three digit number, not a two digit number.

Thus either the 5 is here

_ _ _ = 5 _

or here

_ _ = 5 _

Hence in one of the equations the number on the right is 51, 52, 53, 54, 55, 56, 57, 58 or 59.

In an orderly way see how you can write each of these as a product of two 1 digit numbers or a 1 digit number times a 2 digit number with no digit repeated, and then see if you can form the second equation from the remaining digits.

Penny