Arithmetics question, so confused :(

Hi guys & Girls Ive come across this question in my assignment for math, surely i dont have enough information to get an answer?

The Sum of the first **10** terms of an arithmetic series is **165** and the sum of the next **10** terms is **445**. Find the sum of the terms **21-30**.

SUM = n/2 [2a (n-1)]d

**n**= number of terms (10 for each formula as only 10 terms are added together i.e. **1**->**10** =** 10 and 11**->**20** =** 10**???)

**a =** First Term in series (None given)

**d **= Common difference (also not given)

445 = 20/2 [2a (20-1)]d

165 = 10/2 [2a (10-1)]d

can't use linear equation there because **a** for the **445** will be different from **a** for **165,** and **d** isnt known

all the other formulae i have come across either require **d** or at least a couple of values in the sequence so I can work out **d**

pfft, surely it's impossible? (Doh)