Round 198.4 to 3 significant figures

To round to 3 sign. fig. you have to look at your fourth figure, is it between 0-4? If yes, then it´s should be rounded down. Is it between 5-9? If no, then it´s should be rounded up.
Now, in this case the fourth figure is 4, meaning it should be rounded down..
198 is therefore your D
Have a nice day

To round to any amount of significant figures, you want to count how many numbers there are, and take into account the amount of significant figures. In this case it would be 198, because you wouldn't round the number. In future reference, if a zero is after a decimal (198.0) the zero is considered a significant number. If the zero is sandwiched between two numbers (101) it is significant. You can always use expanded notation if the number is too big to round (1570000 rounded to 3 significant figures would be 1.57x10^6) expanded notation is a bit tricky and you can definitely find some helpful YouTube videos that will go more into depth. I hope this was helpful!

Igot the answer of 15.8 years.