How do you round 105 to the nearest hundred?

1 Answer
Oct 22, 2016

100

Explanation:

Showing what I call the cut off point (in red)

In your mind only write the number as:

#1" "color(red)(|)" "0" "5#
#" "color(white)(.)color(red)(uarr)#
#color(red)("cut off point")#

The digit to the right of the cut off point is less than 5 so we round down. That is, change all the digits to the right of the cut off point as 0 so:

105 is 100 to the nearest one hundred.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#color(blue)("Foot note")#

If the digit to the right of the cut off point had been 5 or more then we would have 200 to the nearest one hundred

Suppose it had been 163

6 satisfies the condition of 5 or more so the digit to the LEFT of the cut of point has 1 added to it.

Consider to the nearest 10

#12 -> "nearest 10 "=10# Rounding down
#13 -> "nearest 10 "=10# Rounding down
#14 -> "nearest 10 "=10# Rounding down

#15 -> "nearest 10 "=20# Rounding up
#16 -> "nearest 10 "=20# Rounding up
#17 -> "nearest 10 "=20# Rounding up
#18 -> "nearest 10 "=20# Rounding up
#19 -> "nearest 10 "=20# Rounding up
#20 -> "nearest 10 "=20# No rounding
#21 -> "nearest 10 "=20# Rounding down
#22 -> "nearest 10 "=20# Rounding down
#23 -> "nearest 10 "=20# Rounding down
#24 -> "nearest 10 "=20# Rounding down

#25 -> "nearest 10 "=30#