Grade
1

How Many Are Hidden? Red Fish, Blue Fish

The number of fish in both pictures is the same.

How many fish are hidden behind the rock? How do you know?

How can you finish the equation to make it true?

The picture on the left shows 10 blue fish and 7 red fish. The picture on the right shows 15 blue fish and a rock with a red question mark. The equation is blue 10 + red 7 = blue 15 + red blank.

What do you notice about how the blue number changed? What about the red number?

In the equation blue 10 + red 7 = blue 15 + red blank, the 10 changed to 15. How does the 7 change when this equation is true?
  • Now there are more than 17 fish in both pictures. You get to decide how many!
    How many fish could be hidden behind each rock? How do you know?
  • Complete the equation to make it true.
    What do you notice about how the numbers changed?
The picture on the left shows a rock with a blue question mark and 15 red fish. The picture on the right shows a rock with a blue question mark and 10 red fish. The equation is blue blank + red 15 = blue blank + red 10.
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