To round a number to a particular digit, look at the digit immediately to the right of your target. If that digit is 4 or lower, zero it and everything to the right of it out. If that digit is 5 or higher, increase the target digit by one and zero everything to the right of it out. If your target digit is a 9, increasing it will turn it to zero and increase the digit to the left of it by one.
100 is already rounded to one significant figure.
It then is 40000 to one significant figure
10000000
9000
It is 10
Round 12 to 1 significant figure is 10.
100 is already rounded to one significant figure.
200 Explanation: 2 is the one significant figure. The zeros are not significant. Round up because it is closer to 200 than to 100.
It then is 40000 to one significant figure
It is 0.01
7000
2,000
8.87
It is: 8.7
0.9
0.1
10000000