Multiplication Using Two Reference Numbers 105
(200 × 0.4) 189 × 77 = 7,260
–11
–3
14,520
–4.4
- 33
14,553 Answer
It is interesting and fun to try diff erent strategies to fi nd the easiest
method.
Test you rself
Try these for yourself:
a) 92 × 147 =
b) 88 × 172 =
c) 94 × 68 =
d) 96 × 372 =
The answers are:
a) 13,524 b) 15,136 c) 6,392 d) 35,712
How did you do? I used 100 × 1½ for a), 100 × 1¾ for b), 100 × 0.7 for
c) and 100 × 3¾ for d).
By now you must fi nd these calculations very easy. Experiment for
yourself. Make up your own problems. Try to solve them without
writing anything down. Check your answers by casting out the
nines.
What you are doing is truly amazing. You are certainly developing
exceptional skills. Keep playing with the methods and you will
fi nd it easier with practice to do everything in your head. You are
developing great mental and mathematical skills.