Some coins were arranged in a row.
Half of them were tails up.
Two of the coins are turned over and now one third of them are tails up.
How many coins were in the row?

Teacher: Here is a visual aid to use if required. Coins can be dragged and, to turn them over, doubleclick.

Have a guess!

Topics: Starter | Fractions | Problem Solving | Puzzles

• Mrs A Milton, Ysgol Ardudwy
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• I have used your starters for 3 years now and would not have a lesson without one! Fantastic way to engage the pupils at the start of a lesson.
• The Best Maths Group Ever 7cd/M2, King Alfred's College, Oxfordshire
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• Some of us caught on quickly. But majority found it tricky. Drawing coins helped to explain the answer.
• Rachel, Claverham
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• You should have been more specific with the wording and said that the tails were turned over.
• Francis, Halifax
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• The wording of the question is fine. If 1/2 of the coins start as tails up, and, when 2 are turned this becomes 1/3, it should be obvious that it was tails that were turned because 1/3 is less than 1/2.
• Gabriel, Edgware
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• The wording is a problem...
If you started with 6 coins and turned one head and one tail over, you would get to 1/2 and 1/3.
Surely?
• Primary 7, Bargeddie Primary School
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• The majority of our class found this very confusing at first. However, Lewis in our class worked out the answer very quickly: he worked out that if he thought of a number on the 2 times table, and tried to take 2 away to see if it was on the three times table then he would have his answer...
The rest of the class were most impressed!
• Nick, Weston
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• This was epic.
• Sarah, Tenbury
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• I think your algebraic answer is harder than it needs to be. if you say
x/2 - 2 = x/3 (+2 and -x/3 on both sides then

x/2 - x/3 = 2 (x6 both sides)
3x - 2x = 12 so x=12.
• Mr Miller, Brough Primary
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• One child in our class found this particularly confusing but she eventually understood after much discussion and debate with the teacher!
Everybody else found it interesting, if not challenging.
• Holly Walton, Calmore Junior School
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• Really good website.
• Matthew Zhao, 5S, Craigslea State Primary School
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• Challenging for average grade 5s, although very easy for my intelligent brain and my quick way of using Trial and Error. =).

How did you use this starter? Can you suggest how teachers could present or develop this resource? Do you have any comments? It is always useful to receive feedback and helps make this free resource even more useful for Maths teachers anywhere in the world.

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