Question Video: Finding the Missing Number in an Arithmetic Sequence of Decimals Mathematics • 5th Grade

What is the missing number? 0.1, 0.3, _, 0.7, 0.9.

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Video Transcript

What is the missing number?

Our sequence of numbers is this: zero and one tenth, zero and three tenths, a missing value, zero and seven tenths, zero and nine tenths. To solve for the missing number, we’ll need to find out what operation is happening at each step.

Going from one tenth to three tenths is an increase. It’s going up. This tells us that we’ll likely need to add. One tenth plus some number equals three tenths. I know that one plus two equals three. And that means one tenth plus two tenths equals three tenths.

We think that the pattern here is adding two tenths. But let’s check with the other values that we have. To move from seven tenths to nine tenths, do you add two tenths? It would look like this: seven tenths plus two tenths does equal nine tenths.

Now we’ve determined our pattern. Our pattern here is adding two tenths every time from one tenth to three tenths. So to solve for our missing number, we’ll need to add two tenths to the three tenths, zero and three tenths plus zero and two tenths. Three plus two is five. Bring down the decimal. Zero plus zero equals zero. The missing value is zero and five tenths.

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