# Weighing stations

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Purpose

In this unit students work at a variety of stations involving practical measuring tasks. Estimation skills and the ability to measure accurately using kilograms and grams are developed.

Achievement Objectives
GM2-1: Create and use appropriate units and devices to measure length, area, volume and capacity, weight (mass), turn (angle), temperature, and time.
Specific Learning Outcomes
• Estimate weight in kilograms and grams.
• Measure accurately using kilograms and grams.
Description of Mathematics

Students' measurement experiences must enable them to:

• Develop an understanding of the size of the standard unit.
• Estimate and measure using the standard unit.

This unit builds on students personal benchmarks and provides students with the opportunity to extend their understanding of the units of mass by exploring measurement tasks within everyday contexts.

This unit provides an opportunity to discuss strategies that can be used to solve comparison problems.

In the activities at the stations students are asked to estimate and then measure the weights of a variety of objects. Encourage students to work out the difference between their estimate and the actual measurement, and then ask them about this.

• How did you work out the difference between your estimate and the measurement?
• Can you think of another way to work that out?

Students may count on or back, or they may be able to use partitioning strategies. For example:

• I estimated the packet would weigh 157 grams and it actually weighed 165 grams; 158,159, 160, 161, 162, 163, 164, 165 that’s 8 grams difference.
• I estimated the bag would weigh 260 grams and it actually weighed 285 grams. 260 and 20 more would be 280 and then another 5 make 285. 20 and 5 make 25 so there’s 25 grams difference.
Required Resource Materials
• Station One: Boxes and containers from grocery items, sand, kitchen scales, Copymaster One.
• Station Two: Small to medium size boxes with contents of varying weights, bathroom scales, Copymaster Two.
• Station Three: Plastic bags, grocery items from the bulk bins e.g. lentils and kidney beans, kitchen scales, Copymaster Three.
• Station Four: Grocery items of varying weights (e.g. cans of fruit, boxes of cereal and bags of sugar), cover the information on the packet regarding the weight of the item with masking tape), kitchen scales, Copymaster Four.
• Station Five: Equipment and ingredients to make Lolly Cake, (recipe on Copymaster), Copymaster Five.
Activity

#### Prior experience

Prior to this unit, students need to have plenty of experience developing benchmarks for measures. Units such as Making Benchmarks - Mass provide opportunities for this.  They should also have been introduced to reading simple scales.

#### Station One

In this station students fill up boxes and containers from everyday grocery items, estimating their weight according to the information on the packet. They check their estimations by measuring.

Copymaster One

Choose a box or packet to work with.

1. Read the information on the box to find out the weight of the packet when it was full.
2. Use the sand. Fill up the packet until you think it weighs the same amount as when it was first bought.
3. Check your estimate by weighing the packet on the scales.

Record your work in a table.

 Packet Original Weight My Estimate

#### Station Two

In this station students estimate then measure the weight of different parcels to be sent in the post.

Copymaster Two

1. Choose one of the boxes to work with.
2. Pick it up and estimate its weight. Record your estimate.
3. Use the scales to weigh the box. Record the weight.
4. Compare your estimate with the actual weight. How close were you?
5. Use the table to work out how much it would cost to send your parcel somewhere in New Zealand to arrive the next day.

Pricing and Information

 Service Delivery Price per Unit (incl GST) NATIONWIDE - Post 1-3 day delivery \$2.50 up to 500g \$2.95 up to 1kg NATIONWIDE - FastPost Next Day \$3.10 up to 500g \$3.50 up to 1kg

Record your work on a table like this.

 Box Estimated Weight Actual Weight Price to Post

#### Station Three

In this station students fill up bags with grocery items from the bulk bins, estimating their weight according to a shopping list. They check their estimates by weighing the bags.

Copymaster Three

1. Write a shopping list for a partner. Choose from the bulk bin grocery items to make your list and make sure you specify how much of each item you will need.

For example:

Shopping list

200g red lentils
300g brown lentils
150g kidney beans
500g chick peas

1. Swap lists with your partner. Fill a bag for each item on your partner’s list, estimating the weights required.
2. Check your estimates by weighing the bags on the scales.

#### Station Four

In this station students estimate the weight of everyday grocery items. They weigh the items to check their estimates then compare the actual weight with the weight stated on the packaging. Make sure you put masking tape over the weights of the products to encourage estimation.

Copymaster Four

1. Choose a grocery item to work with.
2. Estimate the weight of the item and record.
3. Measure the weight of the item using the kitchen scales and record this.
4. Check the weight of the item using the information on the packet.
5. Compare your three weights – estimated, actual and stated. Are they different? If so, why?

Record your work on a table like this.

 Item Estimated Weight Measured Weight Weight as stated on packaging

#### Station Five

In this station students measure ingredients accurately to make Lolly Cake.

Copymaster Five

Make Lolly Cake using this recipe. Be sure to measure your ingredients carefully!

Lolly Cake

Ingredients:

120 g butter
250 g malt biscuit crumbs
180 g fruit puffs
1/2 tin condensed milk
coconut – for coating

Method:

1. Warm butter and condensed milk together in the microwave.
2. Add biscuit crumbs and fruit puffs.
3. Stir well.
4. Roll into one log or small balls. Coat in coconut.