A student measures the volume of a liquid and finds it to be 40ml. How many significant figures are in the measurement ? Really confused can someone help me out ?

Answer 1

there is no decimal point , so the "4" is the only significant digit

non-zero digits are significant

zeroes are significant in some cases
... between non-zero digits ... 2001 , 4 sig fig
... trailing zeroes with a decimal point ... 400 , 1 sig fig ... 400.0 , 4 sig fig