It would appear to have 2 significant figures,
but if there is a decimal place after the 0 (so, 150.) then it is three.
An infinite number of numbers would round to 150.
2 significant figures.
The number whose farthest right significant digit determines it. Whatever place that digit is in is the last significant digit in the sum. For example: 433 + 150 + 3.67 + 8000 = 8586.67, but in sig figs this is only 9000, as the thousands digit is the lowest digit that can be represented.
231.57 has five significant figures/numbers. All the numbers in 231.57 are significant.
2
Infinitely many. There are infinitely many numbers between any two numbers. So, for example, cosidering only the numbers that round up, there are an infinitely many numbers between 149.999 and 150, all of which would round to 150. And there are another infinity between 149.5 and 149.999 which, to the nearest unit would round to 150. If you are rounding to the nearest 10, all the numbers between 145 and 150 would also round to 150. In all cases you must also consider the numbers that are rounded down to 150.
There are 600 5-digit numbers divisible by 150.
150/8 = 18.75 so 18 numbers.
The figure 18.03 has a total of four significant numbers
There are 29 numbers between 1 and 150 that are divisible by five.
Three. All nonzero numbers are significant, and any zeros in between significant numbers are significant.
Because 10.00400 is 10.004, this has five significant digits (numbers).