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Singapore 6th Grade Math Lesson 7
Whole Numbers

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Math Lesson 7: A Froggy Question

Freddy Frog and his brother, Brady Frog, went hunting for flies last night. As Freddy had a longer tongue, he caught 30 more flies than Brady. When they went back home with their catch, sneaky Freddy stole a further 25 flies from Brady. Freddy had thrice as many flies as Brady after that. How many flies did each of them catch in the beginning?

Let's Solve It!

Please draw the following diagram on a piece of paper. By drawing along with me, you will be better able to understand how I solve this problem.

In the beginning, Freddy caught 30 more flies than Brady. This is how our diagram will look like.

Then, Freddy stole 25 flies from Brady. I colored part of Brady's model blue to show that it is no longer with him. That will move from Brady to Freddy - see the direction of the red arrow. However, you don't have to draw the arrow.

Notice in the next diagram that I have lengthened Freddy's model with a dotted box. I also wrote 25 in that dotted box. This shows that he has taken 25 flies from Brady.

We are told that Freddy has 3 times as many flies as Brady after stealing the flies. We can write that down as units in the diagram. Freddy has 3 units and Brady has 1 unit. And the difference between them is 2 units.

Do you think it would be easy to figure out the value of 2 units? If you do, you are right!

Value of 2 units: 25 + 30 + 25 = 80

The next step is to get the value of 1 unit.

1 unit: 80 ÷ 2 = 40

Look at the next diagram. I have written that 1 unit = 40.

It's simple after this. Let's calculate how many flies each frog had AFTER 25 flies were stolen.

Brady: 40

Freddy: 40 + 25 + 30 + 25 = 120

The question asks for the number of flies each frog had BEFORE Freddy stole Brady's flies. We have to deduct 25 from Freddy and add 25 to Brady.

Freddy (deduct 25 because he had 25 fewer flies before he stole some):
120 - 25 = 95

Brady (add 25 because he had 25 more flies before some were stolen from him):
40 + 25 = 65

Singapore Maths Tutoring Online
Grade 6 Lesson 7 Answer

Freddy initially caught 95 flies and Brady 65 flies.

Now it's your turn to answer 3 Interactive Math Questions!

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