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1.23 * 10^-7

Step-by-step explanation:

For decimals smaller than 1 usually something like 0.0000111 you count the decimal places backwards until you get to something greater than 0. So if you have 0.0022 the exponent would be 2.2 * 10^-3

For your problem 0.000000123

There's 6 zeros before you encounter the number thus your exponent is 1.23 * 10^-7

Here's a picture of how to do it!

50 min

step-by-step explanation:

they will be decreasing both their times in half

60 / 2 = 30

40/2 = 20

30 + 20 = 50