CLASS: JSS 1
TERM: 1st TERM
Rounding Off Numbers
Dimensions ,Distances, Capacity and Mass
Rounding off Number
Estimation is making guess of the nearly correct calculation in distance, weight, price or capacity of things without the actual measurement or calculation. Even though it is not accurately done, it gives a good idea of the correct answer.
Estimation help us to have a rough idea of the answer when we add, subtract, multiply or divides given quantity. Sometimes rounding off numbers and approximation are used in making estimation.
1, Round 1234 to the nearest 10
III. Round these numbers to the nearest thousands
Solution to the examples:
iii. 3512 = 4000 to the nearest thousand
Give 474.4547 correct to the nearest hundredth and thousandth
Solution to the example.
474.447 = 474.45 to the nearest tenth
=474.45 to the nearest hundredth
=474.455 to the nearest thousandth.
Round ( I ) 13.73 (ii)34.245 to the nearest whole number
3 Significant Figure:The word significant means important and it is another way of approximating numbers. A figure position in a numbers. A figure’s position in a number show what the figure worth.
Note; That the first significant is always the first non-zero figure as you read a number from left. Again notice that zeros in the middle of a number are significant . Zero before or at the end of another are significant. Measurements and currencies are usually given to a specified number of significant figures.
(a) 1. s.f (ii) 2. s.f (iii) 3. s.f.
(a)1 s.f (ii) 2 s.f. (iii) 3. s.f. (iv) 4 s.f (e) 5 s.f
iii. Give 0.007025 to
(i) 1 s.f (ii)2 s.f (iii) 3.s.f (d) 4 s.f
(a) 2.s.f (b) 2.s.f.
Solution to the examples
= 5800 to 2 sf
=5750 to 3s.f
= 100 correct to 1 s.f
= 150 correct to 2 s.f
=147 correct to 3s.f
= 147.0 correct 4 s.f
= 147.01 correct to 5 s.f
= 0.007 correct to 1 s.f
=0.0070 correct to 2 s.f
= 0.00702 correct to 3 s.f
0.007025 correct to 4 s.f
=0.00070 correct to 2 s.f
=0.000700 correct to 3 s.f
remember that the zeros at the end are necessary to show the number of significant figures.
Solution to evaluationquestions
1.i. 95 = 100 correct to nearest ten
The common units of length(i.e km, m,cm, mm) mass (i.etonne, kg. g ) capacity (i.e cl.ml) and time (hour, min. seconds ) are widely used. The most common unit for length are millimeter(mm) centimeter (cm). Meter(m) and centimeter for short length and the higher units (meter and kilometer) for larger distances.
The common units of mass are the gramme(g), kilogramme kg and tone (t). The common units of capacity and the milliliter (ml) centiliter (cl) and litre (l) as unit length, we use the lower units for smaller quantities.
It is important to be able to choose the most appropriate meter units of measurement to use. For example to measure distance less than a metre,smaller such as millimeter (mm) and centimeters are used. To measure a large distance metres (m) a kilometers (km) are used.
iii. to measure the time it will take to run 200m, we use seconds etc.
1.State the metric units at length you would use to measure the following;
(a) length of your classroom (b) length of your fingernail
(a) your weight (b) the weight of a diary.
a . the time it takes a sportman to run 100m b. the time it takes to walk or travel to your school.
Solution to the examples.
(a) height of a desk (b) height of yourself
(a) a parcel (b) a large land
(a) cup (b) car petrol tank (c)a tin of peak milk (d) the amount of water in a reservoir
a time it takes to fill an empty tank b. the time it takes to travel from Lagos to Ado Ekiti.
New General Mathematics by J.B Channonpg 24 Ex 24C nos 2 c-d
Essential Mathematics pg. 170 Ex.16. 7 nos 1 c-d.
It is important to know the prices of items or goods in your area. This will enable you know the best place to buy a particular item at a reasonable price. In general, the more you buy the more you must pay.
1.James bought 5 exercise books at a bookshop at N50.50 each> How much did he spend.
therefore 5 exercise books will cost N50.50 x 5 = N225.50.
That means he spent N252.25
1 candle cost 19C
therefore 5 candles will cost 19C x 5 =95C
1 tin costs N48.00
Therefore 3 tins will cost N48.000 x 3 = N144.00
1 egg cost 12 eggs will cos N6.00
1 dozen (12) eggs will cost N6.00 x 12 eggs = N72.00
one dozen = N72.00
therefore 1 mango will cost 150.00/30 mangoes =N5
therefore 140 similar mangoes will cost N5 x 140 = N700.00
140 mangoes will cost N700.00
(a)500 (b)520 (c )540 (d) 580 (e) 600
(a) 1.99 (b) 2.00 (c ) 3.00 (d) 4.00 (e) 5.00
(a) 7.000 (b)7.014 (c ) 7.015 (d) 7.0145 (e) 7.0146
(a)0.00005789 (b)0.00005790 (c) 0.00005781 (d)0.000057892 (e)0.00005793.
(a) 45600 (b)45700 (c )45800 (d)45690 (e) 45000.
2.Calculate the total cost of the following :
ii.9 mathematical set at N2500.50
iii. 3 pens at 120.25 each
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