Given: #7.351#
Just for demonstration I am going to insert the part of the number we are interested in inside square brackets.
Write #7.351" as "[color(white)(2/2)7.3]51#
The number immediately to the right of the closing bracket is 5.
The general rule is:
#color(brown)("If the trailing number ( my choice of wording) is 5 or more then we")#
#color(brown)("round up. If the 'trailing number' is less than 5 we round down.")#
#color(brown)("By 'rounding down' they mean that the number part inside the")#
#color(brown)("brackets is left as it is and the number part outside is discarded")#
#" "5>=5" so round up"#
#" "bar(ul(|color(white)(2/2) "So "7.351 =7.4" to 1 decimal place"color(white)(2/2|))| )#
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Just to make the process clearer
Suppose we had #[color(white)(2/2)7.3]21#
#2<5# so we round down giving #7.3#
Suppose we had #[color(white)(2/2)7.3]61#
#6>5# so we round up giving #7.4#
