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## Please please can someone help me with ds1's year 4 maths homework!!!!

(32 Posts)
Doshusallie Fri 20-Sep-13 19:14:42

I am shit at maths and dh is also clueless.

The homework is:

The box has 4 digits the example shows, 5 2
1 9 in a square.

This gives four two digit numbers, 52 (along the first row) 19 (along the second row), 51 (down the left hand column) and 29 (down the right hand column). The sum of these four numbers is 151.

Ds1 has to change the numbers so that the boxes contain four different digits from 1 to 9 that give four 2 digit numbers which sum 100.

The "hint" is you may find it helpful to arrange the four two digit numbers in columns to do the addition and think about what digits you need together a 0 in the units, then look at the 10s....

Any ideas?? Help!!!!

OK, you need 4 digits to ne the units that add up to either 10, 20, or 30, and then another different four numbers to be the tens that add up to either 9, 8 or 7 (depending on your first choice). Does that help/make sense?

..."to be the units"

Oh bugger, no that doesn't work - forget I said anything <<posts maths degree back to Warwick>>

I'll have another go...bear with.....

MrsRajeshKoothrappali Fri 20-Sep-13 19:28:57

24
13

MrsRajeshKoothrappali Fri 20-Sep-13 19:30:20

Scratch that, it's wrong.

Feck, it's really hard..

Fri 20-Sep-13 19:32:03

2 2
2 8

TweaksCrunchyCarrot Fri 20-Sep-13 19:32:53

12,
47

Works through trial and error

Fri 20-Sep-13 19:33:46

Do they have to be four different digits, by the way? If so, my answer is wrong. But my working out was that the grid is:

a b
c d

And 20a + 11b + 11c + 2d = 100

You need to get the b, c and d component to add up to 20, 40, 60 or 80, so that a can be 1, 2, 3 or 4 (as opposed to 3.6 or something).

Doesn't work Mrs K I think, but that's a clue, if the numbers are
a b
c d

then either c and d must both be odd or both even.

Total is
ab
+cd
+ac
+bd

So b+2d+c = 10/20/30
and
2a + c + d = 9/8/7

Fri 20-Sep-13 19:34:57

I think this is tough for year 4, by the way.

Fri 20-Sep-13 19:35:56

Isabella We were thinking along very similar lines there!

Small ripple for Tweaks

Fri 20-Sep-13 19:37:31

MrsRaj - that equals 101.

I'll keep working at it.

Anthracite Fri 20-Sep-13 19:38:49

1 5
4 8

TheFallenNinja Fri 20-Sep-13 19:40:35

Doshusallie Fri 20-Sep-13 19:41:41

Anthracite that can't be fit because then you get a 58 in the right hand column which makes the number too high!!!

Anthracite Fri 20-Sep-13 19:43:24

Ignore that one

2 1
3 8. Works

Doshusallie Fri 20-Sep-13 19:43:36

Argh! Come on mums net am totally relying on you!!!

Doshusallie Fri 20-Sep-13 19:45:04

Anthracite, yes!! That works!! He has to she how many ways he can do it!! Wtaf???

Doshusallie Fri 20-Sep-13 19:45:24

How did you do it?????

Fri 20-Sep-13 19:46:19

Going back to this:

a b
c d

And 20a + 11b + 11c + 2d = 100

11b + 11c must equal an even number (because 20a + 2d always does). So either b or c are both odd or even. To keep them low (and different) we'll say they are 1 and 3. So 11b + 11c = 44 which means you have to make 20a + 2d = 56. If a = 2 and d = 8, that works, so the answer is either:

2 1
3 8

or

2 3
1 8

Both work!

MyBoysHaveDogsNames Fri 20-Sep-13 19:47:21

This appears to be an investigative task, seeing how a child will attempt to find the answer. It is interesting to see how a child approaches this kind of task as you can then see how methodical they are and how they plan their attempt. It is also a good way to gauge their accuracy at adding two 2 digit numbers! So let him/her work it out and see what they come up with.

And why are you doing homework on a Friday night??! Mine are comatose, I am impressed by your dedication!

littlemisssarcastic Fri 20-Sep-13 19:48:13

Agree with Tweaks. (bows to tweaks speedy mathematical ability)

Anthracite Fri 20-Sep-13 19:51:35

a b
c d

a can be either 1 or two
b and c are either two odds or two evens

If a is 1, b and c are 2 and 4. These add up to 86, so d is half of 14, ie 7

If a is 2, b and c are 1 and 3. These add up to 84, so d is 8.

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