Complete these sums. One is done for you. Three plus seven equals 10. 33 plus what equals 40. What plus seven equals 80.
The first sum is done for us. Three and seven makes 10. In the next sum, we need to find the number that we add to 33 to make 40. We already know that three plus seven is 10. And 33 has three tens. So we’ve added three more tens. One ten and three more tens makes 40. Did you spot the pattern in these sums?
The second number in each sum is a seven. And the first number in each sum so far has three ones. And we know that three ones and seven ones makes 10. Now, we know that our final missing number must have three ones. We know that seven and three makes 10. What do we have to add to our 10 to make 80? We know that seven and three makes 10. So if we add seven more tens, we’ll have eight tens or 80.
Three plus seven equals 10. 33 plus seven equals 40. 73 plus seven equals 80. The missing numbers are seven and 73.