Answer:
m ≈ 5 · 10¹ [t]
Step-by-step explanation:
First off we can simply approximate the total mass of all students, which is the average mass times the total amount of students.
[tex]m_{student}=51 [kg][/tex]
[tex]N_{students}=988[/tex]
⇒ [tex]m_{total} = m_{student} * N_{students} = 51*988[/tex]
⇒ m ≈ 50·1000 = 50 000 [kg]
Then, we need to bring it to one significant figure.
The amount of significant figures is the amount of digits after the first non-zero digit in whatever number you have, so for example 0.000001 and 1 both have one significant digit, but 1.00 has three. We only need one significant digit, so we just put one digit before the decimal point and then multiply that by a 10 to the power of something because that is not included in the amount of significant digits. So:
⇒ m ≈ 5 · 10 000 = 5 · 10⁴ [kg]
which, in tonnes ([1 t] = [1000 kg]) comes down to:
m ≈ 5 · 10¹ [t]
