### Crossing the Bridge

Four friends must cross a bridge. How can they all cross it in just 17 minutes?

### Coins

A man has 5 coins in his pocket. Given the clues, can you work out what the coins are?

### Flow Chart

The flow chart requires two numbers, M and N. Select several values for M and try to establish what the flow chart does.

# Simple Counting Machine

##### Stage: 3 and 4 Challenge Level:

Well done to Chris from CSN for a clear explanation on how to solve the first question, and well done to Jake from Crosscrake C.E. School, Louise from Melling St.Wilfreds School and Tristan from St James School for answering the first three questions correctly. Special congratulations go to Rachel from Tatham Fells School who managed to answer all questions correctly. Here are her solutions:

With OR and AND for the switches:

when both switches are off both bulbs are off,
when either switch is on one bulb is on,
when both switches are on both bulbs are on.

With AND and AND for the switches:

when both switches are on both bulbs are on,
the rest of the time - both bulbs are off.

With NOR and NOR for the switches:

when both switches are off both bulbs are on,
the rest of the time - both bulbs are off.

With XOR and OR for the switches:

when both switches are off both bulbs are off,
when one switch is on both bulbs are on,
when both switches are on one bulb is on.