Plenty of Pens

Adrian has worked out this problem very efficiently:

No of pencils $= x$
No of pens $= 4x$

Spent on pencils $= 10x$
Spent on pens $= 4x \times15 = 60x$
Total spent $= 10x + 60x = 70x$

$70x = 250 - 40$
$70x = 210$
$x = 210 / 70 = 3$

Therefore no of pencils $= 3$
No of pens $= 3 \times4 = 12$

Pupils at Moorfield Juniors, including Emma, approached it slightly differently:

We worked this out by taking 40p from £2.50 which is 2.10 then using trial and error.
It was easy because there aren't many low numbers in the 4 times table.
The answer is 12 pens which equals £1.80. 12 divided by 4 = 3 so there are 3 pencils which equals 30p.
£1.80+30p= £2.10.