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### Four Go

This challenge is a game for two players. Choose two numbers from the grid and multiply or divide, then mark your answer on the number line. Can you get four in a row before your partner?

### Shapes in a Grid

Can you find which shapes you need to put into the grid to make the totals at the end of each row and the bottom of each column?

### Follow the Numbers

What happens when you add the digits of a number then multiply the result by 2 and you keep doing this? You could try for different numbers and different rules.

# Forgot the Numbers

##### Stage: 2 Challenge Level:

We had nearly $100$ solutions sent in for this challenge.

From Forest Lake State School in Australia we had contributions from $3$ pupils, Long, Daniel and this is Connor's":

At first I did this:

$46$ divided by $15=3.0666666$
$44$ divided by $14=3.1428571$
$43$ divided by $14=3.0714285$
$42$ divided by $14=3$
$41$ divided by $14=3.1538461$
$39$ divided by $13=3.25$
$38$ divided by $12=3.1666666$v
$36$ divided by $12=3$
$29$ divided by $12=3.2222222$
$28$ divided by $9=3.1111111$
$27$ divided by $9=3$
$26$ divided by $9=3.25$
$25$ divided by $8=3.125$

The last division sum is the correct answer. At first I did $46$ sided by
$15=3.06666666$, so I knew the two numbers had to be lower. When I got down
to $25$, I knew that the dividing number had to be reasonable. So I tried 8.
Hey presto! I got the answer right. Last algorithm - $25$ divided by $8= 3.125$.

Isabella from Sharp school, together with Mellisa and Rebecca had a different way of approaching it:

Firstly I wrote down the 3.125 times table:
$3.125, 6.25, 9.375, 12.5, 15.625, 18.75, 21.875, 25, 28.125, 31.25$
I saw the only whole number was $25$ ($8$ lots of $3.125$) so that means $25$
divided by $8$ is $3.125$.

A number of different approaches were shown by pupils from Rykneld School in the UK. The pupils were, Alice, David, Jordan, Kieran, Daniel, Alicia and Alice who suggested a further challenge:

After we had worked out the solution to the problem, we made our own!

I divided two numbers and got the answer of $13.5$.  I can't remember my two
numbers but they are both under $75$ and are whole numbers.  Can you work out
what my numbers were?

From Huy at the Australian International School of Vietnam we had the following:

We call these two numbers as X and Y.
I know that $3.125$ equals to fraction $3 1/8$.

$X = (3 1/8)$ times Y and Y is the whole number -->   Y must be a multiple of $8$.

Because X and Y are under $50$, I figure out $Y = 8, X = 25$

From Varsity Acres in Canada we had the following message, ( they sent in a pictures of their work but unfortunately we were not able to use it.)

Student work, done in French , a student discovered the connection between $0.125$ and $125$.

$8$ x $125 = 1000$ so - $1.0$!\$ A fantastic leap and she brought the class along.

Well done all of you. I'm sorry we cannot publish all the solutions!

The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities can be found here.
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