jmc

Question

Find 4321_7-123_7+32_7-21_7+1_7. Express your answer in base 7.

Accepted Answer

To avoid borrowing, we switch around the order of the numbers to

432 1_{7} + 3 2_{7} - 12 3_{7} + 1_{7} - 2 1_{7}

.

Now, we can easily find that

432 1_{7} + 3 2_{7} - 12 3_{7} + 1_{7} - 2 1_{7} = 435 3_{7} - 12 3_{7} + 1_{7} - 2 1_{7} = 423 0_{7} + 1_{7} - 2 1_{7} = 423 1_{7} - 2 1_{7} = 421 0_{7} .