# Mental Mondays #10

This is Mental and Oral starter gives children plenty of opportunities to work with a specific 'times table'.

However the focus is on using a range of strategies to solve mathematical problems. It's also quite fun!

You start off by showing the children times table. However, most of the numbers are replaced by letters.

Here's an example using the 9 Times Table:

G x 9 = KH
M x 9 = 9
T x 9 = FB
B x 9 = WT
F x 9 = BF
MZ x 9 = 9Z
W x 9 = HK
H x 9 = MG
9 x 9 = GM
K x 9 = TW

Not only are most of the numbers replaced by letters but the times table is not in numerical order. The challenge, of course, is for the children to use whatever strategies they feel appropriate to try to identify the 'coded' numbers.

For example, the children may quickly notice that the second line shows M x 9 = 9. Clearly, then M = 1.

This can be proven by looking at the second to the last row, 9 x 9 = GM. Since 9x9 is 81, G = 8 and M = 1.

Now we know about G and M, maybe that will help somewhere else... the next line above shows H x 9 = MG; so now we have learnt that H must be 2.

F x 9 = BF is also a useful line... what number (represented by F) when multiplied by 9 appears in the units (ones) column of the product? Only one number works in this situation: 5, 5 x 9 = 45. So F must be 5, and we have also learnt that B is 4.

If children have some confidence with the 9 times table, and can use a number of problem solving strategies, the completion of this times table should be a fairly rapid affair.

After a few minutes, ask the children to share their findings and to discuss their strategies and their thinking.

Here's the solution:

8 x 9 = 72
1 x 9 = 9
6 x 9 = 54
4 x 9 = 36
5 x 9 = 45
10 x 9 = 90
3 x 9 = 27
2 x 9 = 18
9 x 9 = 81
7 x 9 = 63

A follow-up activity could be to encourage a pair of children to 'encode' a times table for another pair to 'crack'. alternatively, you could simply challenge them to decode one of the following times tables as quickly as they can.

Here are the remaining times tables, should you want to use them you can copy and paste them off of this page. We haven't included the 10x table... maybe you could challenge your children to find out why the 10x table cannot be coded (or decoded) satisfactorily?

E x 2 = T2
D x 2 = TA
R x 2 = A
A x 2 = I
TF x 2 = 2F
T x 2 = 2
W x 2 = E
C x 2 = TF
I x 2 = TE
H x 2 = TI

6 x 2 = 12
7 x 2 = 14
2 x 2 = 4
4 x 2 = 8
10 x 2 = 20
1 x 2 = 2
3 x 2 = 6
5 x 2 = 10
8 x 2 = 16
9 x 2 = 18

G x 3 = TP
V x 3 = KT
K x 3 = G
A x 3 = TK
TU x 3 = 3U
T x 3 = 3
3 x 3 = S
W x 3 = TW
P x 3 = KA
S x 3 = KV

6 x 3 = 18
7 x 3 = 21
2 x 3 = 06
4 x 3 = 12
10 x 3 = 30
1 x 3 = 03
3 x 3 = 09
5 x 3 = 15
8 x 3 = 24
9 x 3 = 27

Z x 4 = DA
CR x 4 = WR
S x 4 = DR
A x 4 = ED
C x 4 = W
W x 4 = CY
Q x 4 = EY
D x 4 = A
Y x 4 = DW
E x 4 = CD

7 x 4 = 28
10 x 4 = 40
5 x 4 = 20
8 x 4 = 32
1 x 4 = 4
4 x 4 = 16
9 x 4 = 36
2 x 4 = 08
6 x 4 = 24
3 x 4 = 12

F x 5 = K5
T x 5 = KP
L x 5 = 5
5 x 5 = M5
U x 5 = O5
M x 5 = LP
LP x 5 = 5P
K x 5 = MP
O x 5 = L5
H x 5 = OP

9 x 5 = 45
8 x 5 = 40
1 x 5 = 5
5 x 5 = 25
7 x 5 = 35
2 x 5 = 10
10 x 5 = 50
4 x 5 = 20
3 x 5 = 15
6 x 5 = 30

G x 6 = VG
L x 6 = TG
T x 6 = BR
F x 6 = 6
FR x 6 = 6R
B x 6 = FU
V x 6 = FV
U x 6 = GU
H x 6 = B6
J x 6 = GV

4 x 6 = 24
9 x 6 = 54
5 x 6 = 30
1 x 6 = 6
10 x 6 = 60
3 x 6 = 18
2 x 6 = 12
8 x 6 = 48
6 x 6 = 36
7 x 6 = 42

7 x 7 = RA
W x 7 = PL
G x 7 = 7
R x 7 = NW
A x 7 = LU
P x 7 = UP
N x 7 = GR
GS x 7 = 7S
L x 7 = RN
U x 7 = NG

7 x 7 = 49
8 x 7 = 56
1 x 7 = 7
4 x 7 = 28
9 x 7 = 63
5 x 7 = 35
2 x 7 = 14
10 x 7 = 70
6 x 7 = 42
3 x 7 = 21

L x 8 = Z8
P x 8 = TL
V x 8 = DL
Z x 8 = CV
DE x 8 = 8E
D x 8 = 8
C x 8 = VZ
T x 8 = ZE
Y x 8 = LZ
H x 8 = PV

6 x 8 = 48
7 x 8 = 56
2 x 8 = 16
4 x 8 = 32
10 x 8 = 80
1 x 8 = 08
3 x 8 = 24
5 x 8 = 40
8 x 8 = 64
9 x 8 = 72

## Comment viewing options

### Thanks - what a great idea

Thanks - what a great idea I'm going to try this for my higher ability students as one of their taskboard activities in Maths - some of the easier tables I will use for the lower groups.
0 users have voted.

### Really good idea to help

Really good idea to help with problem solving and also multiplication knowledge.  I plan to use it on Wednesday :)
0 users have voted.

### What a fantastic idea and

What a fantastic idea and resource! Thank you - this will be great for starters and group activities. My Year 4's will love the challenge!
1 user has voted.

### Great idea My class will love

Great idea My class will love the challenge of solving these problems, using their tables
0 users have voted.

### Fabulous ideas.  I tried the

Fabulous ideas.  I tried the x2 with my Y5 class to try and boost their problem solving skills.  It took a while for them to get the hang of the progression and the logical order for solving each clue but they really loved it.  Now they've got the hang of it I'm going to give them opportunities to solve the other puzzles too!
2 users have voted.

### I can't wait to try this with

I can't wait to try this with my year 4/5 class. We have specific time in our timetable for times tables practice and this will really engage some of the more able children who are already pretty competent with their times tables. This will also get them into problem solving mode which is just what some of the children need. Brilliant!
1 user has voted.

### Excellent resource which all

Excellent resource which all abilities in my mixed year 4/5 class enjoyed getting their teeth into!
0 users have voted.

### Exactly what i want from an

Exactly what i want from an intensive task...thankyou
1 user has voted.

### Very clever - think my adult

Very clever - think my adult classes will also find this fun and a challenge Thanks!
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### Brilliant resource - will

Brilliant resource - will really engage my class - especially my lower ability children who will enjoy looking at the patterns!  Thank you!
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### Inspired! I can't wait to try

Inspired! I can't wait to try this - fits in so well with my children's obsession with being detectives. thank you!
0 users have voted.

### I really like this idea -

I really like this idea - will use the worksheets as consolidation or homework. really makes the children think mathematically. Can be adapted for different abilities too.    Thank you
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### Good idea. I have adapted it

Good idea. I have adapted it to provide an independent activity to challenge some of my most able Y3s who know their tables really well while I do a weekly tables test with the others - I've made the ones for 6, 8, 7 and 9 tables into worksheets they can use. Hope that's ok. If anyone would like to see them they are here (I will take them down if you don't want me to have these up, just thought they might help someone) dl.dropbox.com/u/10768247/Crack%20the%20Code%20answer%20sheets.pdf dl.dropbox.com/u/10768247/crack%20the%20code.pdf
2 users have voted.