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7/29/2019 Gene Maths 2
1/8
Prof. M A ThiruthuvadossCell: 9445204774
for Excellence in Mathematics
http://www.magicmaths.org
REFORMMuch Needed
LongOverdueand
A Genuine
PutMATHSBACK
ONTRACK
Savethe Children&
MATHEMATICS!
Formula FactoryTamilnadu Std. VIII Text-Book
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Formula Factory (TAMILNADU STATE BOARD TEXT-BOOK STD VIII - 2011-12)
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The 9-member (Text-Book) Committee ofTamilnadu
that prepared the above text-book has really done
A great service to the entire humanity.
They have successfully invented/identified 39 Rules and Formulae.
So that VIII Standard children may easily and instantly calculate
C.P., S.P., M.P., L.P.,
PROFIT/GAIN, LOSS, PROFIT/GAIN PERCENTAGE, LOSS PERCENTAGE,
SIMPLE INTEREST,
COMPOUND INTEREST FOR FRACTIONAL PERIODS LIKE 3 YEARS(INTEREST BEING COMPOUNDED HALF-YEARLY) ETC. ETC.
By Mugging up these 39 results
The children will get All the Life skills needed and live happily for the rest of their lives.
Sincere Congradulations for such a mighty contribution to Society & Mathemataics
Our ELDERS who were not that smart after all, used only 2 formulae namely
Simple interest =P n r
100
Compound Interest
Amount at the end of nth year is A = P
nr
1100
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Formula Factory (TAMILNADU STATE BOARD TEXT-BOOK STD VIII - 2011-12)
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Chapter 3: Life MathematicsPercentage, Application to Profit, Loss, Interest
3.1 Introduction3.2 Revision: Profit, Loss and Simple Interest Pages 95 - 96
RESULTS ON PROFIT, LOSS AND SIMPLE INTEREST
(i) Profit or Gain = Selling price Cost price
(ii) Loss = Cost price Selling price
(iii) Profit % =Profit
x 100
C.P.
(iv) Loss % =Loss
x 100C.P.
(v) Simple Interest (I) =Principal x Time x Rate
100=
Pnr
100
(vi) Amount = Principal + Interest
Example 3.5... ... ...
Remember
Percentage of increase =Increase in amount
x 100Original Amount
Percentage of decrease =Decrease in amount
x 100Original Amount
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3.3.2 Application of Profit and Loss Pages 99 - 100(i) Illustration of the formula for S.P.
Consider the ... ...
S.P. = C.P. + Profit
... ... ...
Selling price (S.P.) =(100 + Profit %)
x C.P.100
(ii) Illustration of the formula for S.P.
Consider the ... ...
We know S.P. = C.P. + Profit
... ... ...
C.P. =100
x S.P.(100 + Profit %)
We now summarize the formulae to calculate S.P. and C.P. as follows:
1. When there is profit 1. When there is a loss
(i) C.P. =100
x S.P.(100 + Profit %)
(i) C.P. =100
x S.P.(100 - Loss %)
2. When there is profit 2. When there is a loss
(ii) S.P. =(100 - Loss %)
x C.P.100
(ii) S.P. =(100 - Loss %)
x C.P.100
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3.3.4 Application of Discounts Pages 105-108
Discount is the reduction on the Marked Price orList Price of the article.
The normal pricr attached to the article before the discount
made is called as Marked Price (M.P.) or List Price of the article.
... ... ...
Hence we conclude the following:
Discount = Marked Price Selling Price
Selling Price = Marked Price Discount
Marked Price = Selling Price + Discount
Example 3.13[After a tedious solution, a formula-method is offered as a better option. - Prof. Doss]
M.P. =100
x S.P.(100 - Discount %)
Example 3.14[After a tedious solution, a formula-method is offered as a better option. - Prof. Doss]
M.P. =100 + Gain%
x C.P.(100 - Discount %)
Example 3.15[After a tedious solution, a formula-method is offered as a better option. - Prof. Doss]
C.P. =(100 - Discount %)
x M.P.100 + Gain%
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Formula Factory (TAMILNADU STATE BOARD TEXT-BOOK STD VIII - 2011-12)
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3.3.5 Application of Tax Pages 109-116
... ... ...
Calculation of Sales Tax
Amount of Sales Tax =Rate of Sales Tax
x Cost of the item100
Rate of Sales Tax =Amount of Sales Tax
x 100Cost of the item
Bill Amount = Cost of the item + Amount of Sales Tax
3.4 Compound Interest
... ... ...
Simple interest =P x n x r
100
Compound Interest
Amount at the end of nth year is A = P
nr
1100
C.I. at the end of n yeas is given by A P
(i.e.) C.I. = P
nr
1 100
P
To Compute Compound Interest
Case 1: Compunded Annually
Here A = P
nr
1100
and C.I. = A P
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Compound Interest Page 117
Case 2: Compunded Half-Yearly (Semi-Annually)
When the interest is compounded Half-Yearly, there are two conversion periods in a year each after 6 months. In such sitations, the
Half-Yearly rate will be half of the annual rate, that isr
2
.
In this case, A = P
2n
1 r1
2 100
and C.I. = A P
Case 3: Compunded QuarterlyWhen the interest is compounded quarterly, there are four conversion periods in a year and quarterly rate will be one-fourth of the
annual rate, r4
In this case, A = P
4n1 r
14 100
and C.I. = A P
Case 4: Compunded when time being fraction of a year
When interest is compounded annually but ime being a fraction.
In this case, when interest is compounded annually but time being a fraction of a year, say 51
4 years, ten amount A is given by
A = P
5r 1 r
1 1100 4 100
and C.I. = A P
for 5 years for 1
4year
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3.5 Difference between Simple Interest and Compound Interest Pages 120
When P is the Principal, n = 2 years and r is the Rate of interest,
Difference betweeen C.I. and S.I. for 2 years = P
2
r100
3.5.1 Appreciation and Depreciation
a) Appreciation A = P
nr
1100
b) Depreciation A = P
nr
1100
3.6 Fixed Deposits and Recurring Deposits
To find the formula for calculating interest and the maturity amount for R.D:
Let r% be the rate of interest paid and P be the monthly instalment paid for n monthsl
Interest =PNr
100, where N =
1 n(n 1)
12 2
years
Total Amount due at maturit is A = Pn +PNr
100
3.6.1 Hire Purchase and Instalments
Equated Monthly Instalmen (E.M.I.)
E.M.I. =Principal + Interest
Number of months
Example 3.5 ... ... ...
Monthly Instalment =Total amount
Number of months