Dr. Purchase’s Multiplication Problem
----Alex Boiardi (Y9)
I’ll be explaining how to solve this problem. First, as there are two three digit numbers. THESE numbers must be 0.
Then I noticed that the second column had: 2, 9 and X to add up to 6, as 9+2=11, the numbers in the second column must add up to 16; so 16-11=5 giving me this. Then due to this, I realised that in the last column, it had an equation of X+1(from carried number) which=5---so the answer is 4. Then I realised that I had a number of 45200 which made me think, what numbers multiply to 2? 1x2 so I put a 1 HERE and not a 2 as 5/2 doesn’t give a full number, and since the answer is 1, this means that the top multiple must be 452. This is derived from × 2 . So I thought, what number times by 5 gives a reminder that also ends with a 0 which adds to make 9. I placed 1 in the box and noticed that it wouldn’t work as 1 × 5 doesn’t give a remainder to create 9; so I placed a 2 and then noticed that 2 × 5 = 10 which then means that 2 × 4 = 8 but when the carrying 1 is added, produces a 9-a perfect fit. Since there’s a 2, 2 × 2 = 4 making this.
16
Made with FlippingBook - Online Brochure Maker