Bike gears - these are similar to car gears. Start in the lower gears (1,2,3,4 etc) and use for up hills. High gears (15-21) for down hill. However, my bike has 21 gears, 3 on the left handlebar, 7 on the right. These are the front gears and the back gears. Each number equates to a slightly smaller or larger cog on the wheel. So 7 is the biggest cog, 6 sits on top of 7 and is slightly smaller, 5 on top and again slightly smaller down to 1 with the least amount of teeth on the cog.
It has been explained to me that 1(LH) x 7(RH) basically means you multiply that number for the 'teeth' on the cogs. So that would be gear 7 (a third of the resistance of highest gear). However, setting the gears like that makes it very hard work for the chain as one cog is tiny and furthest from the wheel, the other cog is very big and close to the wheel. The chain that rotates round these cogs is then not running directly next to the bike and rather it is being pulled away from the frame at the front and close to the frame at the back. This can cause the gears to slip or the chain to come off. However, if you set the gears to 2(LH) x 3 or 4 (RH) the total number of teeth is similar at 6 (2 x 3) or 8 (2 x 4). The chain is much happier to rotate as it is running more even and the resistance is roughly the same. So,
Up hills (and poor fitness in my case) = 1-1, 1-2, 1-3
Middle of the road, flat, easy = 2-1 right through to 2-7
Downhill 3-4, 3-5, 3-6, 3-7
The internet.
All websites and internet equipment have an IP address. The original IP addresses that were designed at the beginning run into around 6 billion I believe. We are running out of numbers. However they have now invented a new range which provides 'more numbers than there are grains of sand on the planet' so in theory we will never run out of IP addresses though hypothetically I guess we could. But like phone numbers and vehicle registrations they will just keep inventing new ones. The next problem is storage. I suspect we will continue developing better ways to store more in less space so I cannot see the internet ever running out.