Task on Decimal Operations: Multiplication and Division
By Mr. Reno's class, School 5
Shelley's Salad Haven is taking inventory
of its supplies. Kieran notes the following
amounts of ingredients in inventory: 7 bags
of dry pasta noodles, 2 cases of salami, 8
pounds of croutons, 5 tubs of Italian dressing.
1. How long will each of the ingredients last
if Salad Haven uses the following each day:
0.10 of a bag of noodles
0.10 of a case of salami
0.10 of a pound of croutons
0 .10 of a tub of dressing
Draw diagrams, number sentences, or use
words to show and justify your reasoning.
2. Salad Haven's business is down and now
only uses 0.01 of each ingredient to make
salads each day. Predict how long they would
have each ingredient before running out.
Organize your work so that others can
understand your reasoning. Write in words
what is happening to the number of days in
each situation.
3. Suppose Kieran read the recipe incorrectly
and finds that Salad Haven really uses 0.20
of each ingredient to make salads each day.
How long will each ingredient last? Use
diagrams, numbers, or words to show how
you know.
This is the work that students produced as the
teacher pressed for conceptual understanding
of the mathematics through assessing and
advancing questions. Students essentially
understood that when dividing by a decimal
number less than one, the quotient will be
more than the dividend because either: you
are making groups of an amount less than
one; or you are making less than one group.