Question Video: Marking a Given Number on a Number Line

Video Transcript

Which point on the shown number line represents 69?

We’re given a number line. It starts with the number 42, and the last number is 87. We’re given the next number after number 42 which is 51. The next three numbers are not given, and then we have number 87. So we need to work out the three missing numbers. And then, we need to decide which of the two points shown, points A or point B, represent the number 69.

The first thing we need to do is work out the difference between number 42 and 51. This will help us work out the next three missing numbers. We need to know how much the numbers increase by each time. We’ve drawn a new number line to help us find the difference between 42 and 51. One, two, three, four, five, six, seven, eight, nine. The difference between 42 and 51 is nine. So to find the first of our three missing numbers, we need to add 9 to 51. This is an easy one to do in our heads.

51 and 9 make 60, and 60 plus nine makes 69. This is the number we were looking for on the number line. We know that point B will be nine more than 69. And point B is nine more than 69, which is 78. The point on the number line which represents 69 is point A.

We found the missing numbers on the number line by working out the rule, which was to add nine each time. And we added nine until we reached 69. The point on the shown number line which represents 69 is point A.