Video: Counting in Ones Up to 20 from Any Given Number

What number is missing?

02:57

Video Transcript

What number is missing? Four, what, six, seven. We’re given a picture that shows a sequence of numbers. We can see these numbers shown as digits, four, six, and then seven. And underneath, we can see the same sequence shown in blocks, four blocks, six blocks, and seven blocks. But our sequence isn’t all it seems. There’s a missing number. If we count through the sequence, we can see four, then a big gap where our missing number belongs, and then six and seven. And the question asks us, what number is missing? In other words, what comes after four in our sequence?

We’re given three possible answers to choose from. And we can see those over here. And if we look at these answers quickly, we can see which number is missing. But let’s work it out for ourselves. The only two numbers that are next door to each other that we know already are six and seven. And we know that if we count forwards in ones, we count from six to seven. Seven is the number that comes after six. And so, we know that our missing number must be the number that comes after four when we’re counting in ones. One, two, three, four. What comes next? Five, our missing number must be the number five.

But if we look at our three possible answers, we can see that each one of them shows the digit five. How can we decide which one is correct? Well, we need to count the blocks underneath. We need to show five blocks to match our digit five. Let’s count each group of blocks. In the first group, we have one, two blocks. This doesn’t show the number five at all. Let’s try our second possible answer. In this one, we have one, two, three, only four blocks. Again, this is too small.

It looks like our last answer must be the correct one. Let’s just count to make sure that there are five blocks. One, two, three, four, five blocks. Now, we think we’ve found our missing number. Let’s see whether our sequence makes sense. Four, five, six, seven. We’ve counted forwards in ones and we’ve found that our missing number was the number five. The correct answer is the one that shows the digit five and also five blocks underneath.

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