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Level Three > Number and Algebra

# Don't Ditch the Boat

Keywords:
Student Activity:

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Achievement Objectives:

Achievement Objective: NA3-1: Use a range of additive and simple multiplicative strategies with whole numbers, fractions, decimals, and percentages.
AO elaboration and other teaching resources
Achievement Objective: GM3-1: Use linear scales and whole numbers of metric units for length, area, volume and capacity, weight (mass), angle, temperature, and time.
AO elaboration and other teaching resources

Purpose:

This is a level 3 number and measurement activity from the Figure It Out series. It relates to Stage 6 of the Number Framework.

Specific Learning Outcomes:

find fractions of mass and volume

Required Resource Materials:
FIO, Level 2-3, Number, Don't Ditch the Boat, page 23
scales, measuring jugs, 2 litre plastic bottles filled with water
plasticine or play dough (for the survival slab)
counters (for pills)
Activity:

Providing students with a physical model of the problem, that is, a full 2 litre bottle of water, 1 kilogram of Plasticine or play dough, and a jar of 20 counters, will help them to work through the problem by identifying the important information.
For five sailors, 2 litres of water, 1 kilogram of survival slab, and 20 pills must last for 2 days.
Suggest that students consider each of the rations separately. A logical path to the solution might be:
Five people for 2 days requires 10 equal parts (tenths).

Some students may divide the ratios in half to get a daily amount and then divide this amount into fifths. Similar reasoning can be applied to the situation in question 4, where there are four people in the boat.
2000 mL ÷ 8 = 250 mL per person per day (water)
1000 g ÷ 8 = 125 g per person per day (survival slab)
20 ÷ 8 = 21/2 pills per person per day (vitamins)
Students who are not familiar with metric units are likely to use innovative ways to divide the amounts. For example, eighths of a 2 litre bottle can be found by:

Repeat the pouring with quarters of a bottle to get eighths.