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'Four Go' printed from http://nrich.maths.org/

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Draw a number line on a piece of paper, marked from $0$ to $20$, like this:

number line from 0 to 20

(You could print off this sheet which has several number lines drawn on it.)

This challenge is a game for two players.  The first player chooses two numbers in this grid and either multiplies or divides them.
 

grid of numbers: 2, 3, 4, 5, 10, 12, 25, 36, 100; multiply and divide symbols

He or she then marks the answer to the calculation on the number line.The second player then chooses two numbers and either $\times$ or $\div$, and marks that number in a different colour on the number line.

If the answer is too big or too small to be marked on the number line, the player misses a go.

The winner is the player to get four marks in a row with none of their opponent's marks in between.

What good ways do you have of winning the game?

Does it matter if you go first or second?

[This game is adapted from a SMILE Centre card.]