(29 # _ )
/ \
/ \
/ \
(21 # _) (37 # 50 )
/ \ / | \
/ \ / | \
(7,9,11) (21,23) (29,30) (37,49) (50,100)
Insertion of 8,51,70 would cause the root to split.The "8" will cause two splits, as described in the text of the lesson. It will only fill the root node, though, not cause it to split.
The "51" key would fill up the rightmost leaf.
The "70" key would overfill the rightmost leaf, causing
a split. The key would be passed up into the interior node
which also would be overfilled. This would cause another
key to be passed up to the already full (from the 8 insert)
root node, requiring the split.