we get them eventually (sadly i see them as a challange) but sometimes after we BOTH stare at them for 15 minutes, clearly in the exam he would have to guess!
Staring not allowed. Imediately start making notes, write down possibilities starting with obvious calculations, follows a copy from an old post of mine. There are some 3 stage calculations creeping in, I will post a technique for those when I have a bit more time.
Middle number has been made using the numbers either side.
Same rule must apply for all 3 sets.
Sometimes 1 operation. Sometimes 2.
Second operation can be:
1] + − x ÷ the same number.
3] + − x ÷ the number on the left or right of the middle number.
If the number in the middle is bigger
than the 2 either side then your 1st operation is probably
adding or multiplying.
If the number in the middle is smaller
than at least one of the numbers either side, then your 1st operation is probably
subtracting or dividing.
If after using the 2 obvious operations the rule does not work for the second set do not panic; just start using the other 2 operations.