whirlygig has it spot on with the Constant Practice..
you will soon find short cuts that suit you. With my lad we practice Time/Speed/Distance calculations if we are on the road for any length of time.
ie i'm at 70mph, it's 12 miles to the services, what time will we get there? sort of thing. Do it yourself in your head when you are driving an dcheck go wclose you are.
remember that most nav is done (or was in my day) on 6minute fixes...easy as this is 1/10th of an hour. Keep it simple.
Getting a feel for the order of things is very important, especially if you get the answer right but are a factor of 10 or 100 out
as for the 27 x 43 calculation..keep it simple (first off the answer should be "about" 1200 from ( 30 x 40) - so that is the order of the answer sorted.
Next find the short-cut you prefer, for me i'd go
27 x 43 = (30 x 43) -(3 x 43)
easy to work out what 30 x 43 is , and no need to work out again what 3 x 43 is (in essence you have already done that) and you get 1290 - 129 which is the 1161 answer ( a quick check on order and we are sorted)
halving numbers and the like works too. For some a 2 digit by 2 digit multiplication is a struggle (mentally you have to store many sub-answers and then recall them) and it is this storing and recollection that leads to errors and brain farts. sooooooooooo
anyone can work out 3 x 43 in a flash (129 - just in case you are struggling)
and i'm fair safe to say that 9 x 129 wouldn't be too hard either.
all this is doing is breaking the double digit multiplication (27 x 43) into a couple of easier to manage chunks ;(3 x 43)x9
some folk find subtraction a doddle, others prefer division or multiplication - find your forte and try to stick to it.
oh...and top tip, if you find you are working something out at college/work and are just about to reach for a calculator then don't...at least have a go at working it out in your head first
now does anyone remember how to use log tables?
