Number Patterns

Lesson Plan - Get It!

Audio:

I need your help to find the missing number!

Read the case file below to catch up on the case!

Case File #5402: The Case of the Missing Mailbox

There are four houses in a row on Place Value Avenue. On Wednesday, each house had a mailbox. The numbers on the mailboxes were in a pattern.

On Thursday, the family in the third house moved. And, they took their mailbox with them.

Now, that third house on Place Value Avenue is missing its mailbox! The postman can replace it, but he doesn’t know what number to put on the mailbox.

The other mailbox numbers are:
993, 1003, _______, 1023

Clue #1: The missing number is 10 more than 1003.
Clue #2: The missing number is 10 less than 1023.
Suspect #1: 2003
Suspect #2: 1004
Suspect #3: 1013

Now that you know more about the case, let’s take a closer look at our clues and suspects:

Suspect #1 is 2003. What needs to be added to 1003 to make 2003?
2003 changes the digit in the thousands place. 2003 is 1000 more than 1003. 2003 is not our missing number.

Suspect #2 is 1004. What needs to be added to 1003 to make 1004?
1004 changes the digit in the ones place. 1004 is 1 more than 1003. 1004 is not our missing number.

Suspect #3 is 1013. What needs to be added to 1003 to make 1013?
1013 changes the digit in the tens place. 1013 is 10 more than 1003.
Suspect #3 fits Clue #1. Does it answer Clue #2?

What needs to be subtracted from 1023 to make 1013?
1013 is 10 less than 1023.

Suspect #3 fits Clue #1 and Clue #2. Now, let’s see if it fits in our number pattern:

993, 1003, _______, 1023

Let’s count by 10.
993 + 10 = 1003 Check!
1003 + 10 = 1013 Check!
1013 + 10 = 1023 Check!

1013 is the missing number! This number pattern changes the digits in the tens place.
993, 1003, 1013, 1023

You’ve solved the case! The postman should put number 1013 on the new mailbox for Place Value Avenue. I think you’re ready to open your own detective agency!

Move on to the Got It? section to find your own number patterns.