Question

There are -------- number formula for big friends.

Abacus​

Answer 1

Answer:

In the case of Big friend, we take the bead of value 10 as the reference. To obtain the number from the addition and subtraction on abacus, we operate reference 10 with the small friend. ... Now, we have to add 9 but there are not enough beads left, so we will take the help of big friend as per the formula 'add 10 less 1'.

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