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Brainwave 10

Counterbalance

Scales
A troupe of performers who visit NSW Country Areas Program schools keeps a set of five counter weights to help stagehands move heavy props.
The weights can balance exactly any load that is a multiple of 10kg, from 10kg up to the total of the five weights.
What are the masses of the five weights that meet these conditions and allow the stagehands to counterbalance the max possible load?
What is the maximum load they can counterbalance?
What are the combinations from 10kg to the maximum possible load?

Feature Solution

The feature solution for the problem came from Year 5 Boys from Tottenham CS and Marc, Nader & Amit from Carlton PS

Gold

Year 5 Boys from Tottenham CS
What did you have to find out?
We had to find out the five weights that were used by the stagehands to counter balance the heavy props. Also, we had to find out the minimum and maximum load they could lift. We also had to figure out what weight combinations we would use to lift each multiple of ten.

What materials did you use?
Paper
Pens
Investigation Sheets
Brains
Smart Board
Computer/ Internet
Problem Sheet

How did you think? What strategies did you use? How did you solve this problem?
To solve this problem we used the trial and error strategy- we trialed different weights in the problem, and if they didn't work we took them out and replaced them with other weights. E.g. we did not need 30kg because we could use 10kg and 20kg to make 30kg.

We were constantly checking and rechecking to ensure that we had correct combinations.

We also worked as a group and so communication was very important.

What answers did you come up with?
The weights were - 10kg, 20kg, 40kg, 80kg and 160kg.

The maximum weight that we could lift using the counterweights was 310kg,. this was a combination of all the weights.

We also found out that the weights doubled every new weight.

The combinations we came up with were:

10kg= 10kg

20kg= 20kg

30kg= 10kg + 20kg

40kg= 40kg

50kg= 10kg + 40kg

60kg= 20kg + 40kg

70kg= 40kg + 20kg + 10kg

80kg= 80kg

90kg= 80kg + 10kg

100kg= 80kg + 20kg

110kg= 80kg + 20kg + 10kg

120kg= 80kg + 40kg

130kg= 80kg + 40kg + 10kg

140kg= 80kg + 40kg + 20kg

150kg= 80kg + 40kg + 20kg + 10kg

160kg= 160kg

170kg= 160kg + 10kg

180kg= 160kg + 20kg

190kg= 160kg + 20kg + 10kg

200kg= 160kg + 40kg

210kg= 160kg + 40kg + 10kg

220kg= 160kg + 40kg + 20kg

230kg= 160kg + 40kg + 20kg + 10kg

240kg= 160kg + 80kg

250kg= 160kg + 80kg + 10kg

260kg= 160kg + 80kg + 20kg

270kg= 160kg + 80kg + 20kg + 10kg

280kg= 160kg + 80kg + 40kg

290kg= 160kg + 80kg + 40kg + 10kg

300kg= 160kg + 80kg + 40kg + 20kg

310kg= 160kg + 80kg + 40kg + 20kg +10kg

Marc, Nader & Amit from Carlton PS
What did you have to find out?
We had to find out the masses of the five weights that can counterbalance the maximum possible load. We also had to find out what the maximum load was. Finally we had to find out the combinations of the the weights to counterweight any load.

What materials did you use?
We used the Investigation Sheet supplied, White Board Markers, Whiteboard, our computer, weights to test our solution, a set of scales and our extensive knowledge of Mathematics.

How did you think? What strategies did you use? How did you solve this problem?
We thought using the formula of ( Powers of 2 can summate up to every consecutive whole numeral from the total of the powers and subjacent)so we used the first five powers of 2 which are 1(2 to the power of 0), 2, 4, 8, 16 and since they are multiples of 10, we multiplied them by 10.

What answers did you come up with?
Using the formula mentioned previously, the counterweights weigh 10kg, 20kg, 40kg, 80kg and 160kg. This would mean that the maximum load would be 310kg. The combinations for summating up to every multiple of ten up to 310 are the following weights: 10kg, 20kg, 40kg, 80kg, 160kg.

10=10kg

20=20kg

30=10+20kg

40=40kg

50=40+10kg

60=40+20kg

70=40+10+20kg

80=80kg

90=80+10kg

100=80+20kg

110=80+10+20kg

120=80+40kg

130=80+40+10kg

140=80+40+20kg

150=80+40+20+10kg

160=160kg

170=160+10kg

180=160+20kg

190=160+20+10kg

200=160+40kg

210=160+40+10kg

220=160+40+20kg

230=160+40+20+10kg

240=160+80kg

250=160+80+10kg

260=160+80+20kg

270=160+80+20+10kg

280=160+80+40kg

290=160+80+40+10kg

300=160+80+40+20kg

310=160+80+40+20+10kg


Silver

Commendable contributors to the problem were:
John, Delaney, Caleb, Andrew, Kristy & Cameron from Blighty PS

Bronze
Solutions were also sent in by: