### Tyneside Average Speed

Weekly Problem 12 - 2006
A van travels from Newcastle to South Shields at 30mph and returns at 40mph. What is its average speed?

### Partial Means

From the mean of 64 numbers, and the mean of the first 36 of these numbers, can you work out the mean of the last 28 numbers?

### David and Goliath

Does weight confer an advantage to shot putters?

# For Richer for Poorer

##### Stage: 4 Challenge Level:

In the rich country of Emerald, the average income is £20,000.
In the poorer, neighbouring country of Flint, the average income is £16,000.
Charlie lives in Emerald and earns £18,000 a year.
He moves to Flint and says "I've made both countries richer!"
What does he mean?

Charlie thinks that the average income in both countries has increased.
Can you convince yourself that Charlie is right?

What other effects can moves between countries have on the average incomes?

Describe what is required for moves to:
• increase the average incomes in both countries
• decrease the average incomes in both countries
• increase one whilst decreasing the other

Extension:
Would it be possible for someone to move from Emerald to Flint and reduce the average income in Emerald and double the average income in Flint?