Kids Home Work2

[fever28]

Sorry to say I'm stuck and already asked a very similar question


I know the answer just be looking at it and doing it in my head

But I don't know how to "work it out". 14 9 and 7

Q: mina has 5 more marbles than Kirsty
Kirsty has 2 more than sen
Altogether they have 30

How many does each child have?


I just picked a low number for seb then added 2 then 5
And from that increased seb till it made 30

But that seems clumsy

[Captain2]

Kirsty has X marbles, so
Mina has (X+5), and
Sen has (X-2)

So X + (X+5) + (X-2) = 30
3X = 30-5+2
3X = 27
X = 9

So Kirsty has 9, Mina has 14 ans Sen has 7

[bert_h]

Less mathematical is maybe a bit easier:

Suppose sen had no marbles, then Kirsty would have 2 and mina 7, that makes 9. There are 21 marbles to be added! But if we share them absolutely evenly, then Kirsty will STILL have two more than sen, and mina will STILL have 5 more than Kirsty. An even share of 21 marbles among the three of them is 7 more marbles each, and there's the answer:

(0, 2, 7) + (7, 7, 7) = (7, 9, 14).