This activity is about working out missing numbers in a 100 square.

 

Here is a 100 square. Look at the patterns on it.

 

The first row has the numbers 1 to 10.

The second row has the numbers 11 to 20 etc.

 

When we jump along we add on 1, when we jump down we add on 10. 

 

Also look at patterns going down such as 11, 21, 31, 41, 51 etc....

 

1	2	3	4	5	6	7	8	9	10
11	12	13	14	15	16	17	18	19	20
21	22	23	24	25	26	27	28	29	30
31	32	33	34	35	36	37	38	39	40
41	42	43	44	45	46	47	48	49	50
51	52	53	54	55	56	57	58	59	60
61	62	63	64	65	66	67	68	69	70
71	72	73	74	75	76	77	78	79	80
81	82	83	84	85	86	87	88	89	90
91	92	93	94	95	96	97	98	99	100

 

 

Example

Put these numbers in the correct boxes:

8, 95, 4, 20, 53

 

1			A				B
									C
		D
				E					100

 

 

Let's look at how to find the answers. 

 

A and B are on the top row, which is the ones counting along from 1 to 10, so for these ones we can just carefully count along the top with our finger. 

1, 2, 3, 4 and then our finger is on A. This means that A = 4. 

 

Let's continue counting along from A to find B. 

5, 6, 7, 8, and then our finger is on B. This means that B = 8 

 

To find C, we can continue counting along until we get to the box above C, this is 10. Now we can jump down a row. 

When we jump down a row we add on 10. So if we are on 10 and jump down one row, we add on 10.

10 + 10 = 20 

 

Follow the red below to see how we jumped to C:

 

 

To find D, count along the top row to where 3 would be and then jump down adding on 10 each time until we reach D. 

This means D will be 63.

Here's how we jumped along:

 

 

Finally, let's find E. We need to count along the top row to 5 (until we are above where E is), then we count down to E, adding on 10 each time:

 

 

Wow, that's a lot of work to do! Do you feel ready to have a go at hunting the correct number?

 

 

You can check back to this introduction at any point by clicking on the red help button on the screen.