How do i replace multiple spaces with one space using sed?

[hawksbill]

Man page for sed: https://www.lightnetics.com/post/3334

The sample file being used:

This is my first IP 10.50.20.1
grapes
apples
pears
This is      the first block
oranges
PLUMS

This is my second IP 10.50.20.2
This is my duplicate IP 10.50.20.2
grapes
apples
pears
This is      the second block
oranges
PLUMS

This is my third IP 10.50.20.3
grapes
apples
pears
This is the third       block
oranges
plums

Replace multiple spaces with one space.

$ sed 's/[[:space:]]\+/ /g' samplefile