That is, if ‘c’ is a positive integer, and
if a < b then ac < bc
if a > b then ac > bc
Note that if an inequality is multiplied on both sides by a negative integer then the
inequality changes.
Also note that, if a < b, then -a > -b. Also, if c > d then, –c < -d (a, b, c, d are positive
integers).
The idea may be taught with written examples supported by necessary text material in
Braille. The idea that the negative sign of a number makes it smaller needs to be
explained. The numberline is the best way to teach this idea. Keeping the zero as the
mid point. Let the child understand that every additional unit on the positive side
makes the number bigger (ie., 3 > 2) whereas every unit on the negative side makes it
smaller (ie., –3 < –2) since more ‘minus’ means more ‘dimunitive’ value.
- Metric system
The quantities used to find lengths, capacities, weights of things etc., are called
measures. Several countries have their own system of measures. Of all the available
systems the Metric system of measures is considered as simple and hence most of the
countries in the world use the metric system of measures.
In Metric system, the basic unit of length is meter (m) the basic unit of weight is gram
(g), and the basic unit of capacity is liter (l)
Metric system is also known as decimal system, as it has other sub units in powers of 10.
1000 100 10 1 (unit) 101 1001 10001
Kilo Hecto Deca Meter Deci Centi Milli
Gram
Liter
