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How Many Spots?KS3 Problem Solving

Constructing and solving equations

Problem : How many spots?

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There are 101 spots on two Dalmatian dogs.

One Dalmatian has 25 spots more than the other, how many spots does each dog have?

Worked Solution

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Solution 1: Step 1: Draw a model

Step 2: Use the diagram to calculate how many spots 101 – 25 = 76

76 = the value of the yellow shaded blocks 76 ÷ 2 = 38

Therefore one dog has 38 spots

38 + 25 = 63 Therefore dog two has 63 spots

Worked Solution

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Solution 2: Step 1: Construct an equation

x + (x+25) = 101Step 2: Solve for x ( to find the number of spots on one dog)

2x + 25 = 1012x = 101 - 25

2x = 76x = 38

Therefore dog 1 has 38 spotsStep 3: Calculate the number of spots on dog 2

dog 2 = x + 1dog 2 = 38 + 25

Therefore dog 2 has 63 spots

Question 1

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There are 101 spots on two Dalmatian dogs.

One Dalmatian has 31 spots more than the other, how many spots does each dog have?

Question 2

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There are 101 spots on two Dalmatian dogs.

One Dalmatian has 27 spots more than the other, how many spots does each dog have?

Question 3

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There are 101 spots on two Dalmatian dogs.

One Dalmatian has 33 spots more than the other, how many spots does each dog have?

Question 4

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There are 101 spots on two Dalmatian dogs.

One Dalmatian has 29 spots more than the other, how many spots does each dog have?

Question 5

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There are 101 spots on two Dalmatian dogs.

One Dalmatian has 35 spots more than the other, how many spots does each dog have?

Question 6

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There are 220 spots on two Dalmatian dogs.

One Dalmatian has 62 spots more than the other, how many spots does each dog have?

Question 7

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There are 222 spots on two Dalmatian dogs.

One Dalmatian has 72 spots more than the other, how many spots does each dog have?

Question 8

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There are 224 spots on two Dalmatian dogs.

One Dalmatian has 82 spots more than the other, how many spots does each dog have?

Question 9

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There are 226 spots on two Dalmatian dogs.

One Dalmatian has 67 spots more than the other, how many spots does each dog have?

Question 10

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There are 228 spots on two Dalmatian dogs.

One Dalmatian has 63 spots more than the other, how many spots does each dog have?

Plenary

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Use your mini whiteboards to answer the following questions

Click here for infinite questions

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Spots on Dog 1 Dog 2

Q1 35 66Q2 37 64Q3 34 67Q4 36 65Q5 33 68Q6 79 141Q7 75 147Q8 71 153Q9 67 159

Q10 63 165

Back to beginning

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Draw a model

Back to Problem