Chapter 4 – Mathematics 7

BPK Penabur GSBy : Mr . Ronald Naradus S

*SOCIAL ARITHMETIC

GLOSSARY

• Cost, Buying price = harga pembelian , biaya• Selling price = harga penjualan• Profit, gain = laba/untung• Loss = rugi• Marked price, original price = harga kotor, harga sebelum didiskon• Discount = potongan harga, rabat, diskon• Sale price, cheaper price = harga bersih, harga setelah didiskon• interest = bunga• interest rate = suku bunga• Simple interest = bunga tunggal• Compound interest = bunga majemuk• Bruto = Berat kotor• Netto = berat bersih• Tarra = Berat bungkus• Principal = Modal mula-mula

Profit and Loss

Selling price > Buying price (cost)

Buying price (Cost ) > Selling price

Profit / Gain

Loss

PROFIT ( Selling Price > Buying Price )

• Profit = Selling Price – Buying Price (Cost)• Buying Price = Selling Price – Profit• Selling Price = Buying Price + Profit

• Loss = Buying Price – Selling Price • Selling Price = Buying Price – Loss• Buying Price = Selling Price + Loss

LOSS ( Buying Price > Selling Price )

Example 1 ! Pg 43 no 1Copy this table into your book and fill the blank!

Buying Price Profit/ Loss / Equal Selling Price

Rp 25.000 Profit Rp 3500

Rp 14.000 Loss Rp 1750

Profit Rp 2250 Rp 34.500

Rp 34.500 Rp 35.400

Loss Rp.2250 Rp 25.250

Rp 17.500 Rp 16.250

Rp 28500

Rp 12250

Rp 32250 Profit Rp

900Rp

27500 Loss Rp 1250

Example 2 ! Pg 43 no 5 A fruit seller buys

650 oranges for Rp 78000. he sells 400 oranges at Rp 200 each and 200 oranges at Rp 150 each. If the rest are not sale because they are rotten, calculate the profit or loss!

Answer Buying price : Rp 78000Selling price :(400 x Rp 200 ) + ( 200 x Rp 150 ) Rp 80000 + Rp 30000 Rp 110000

Profit = Selling price – Buying price

= Rp 110000 – Rp 78000

= Rp 32000

Example 3! Page 43 no 2Adi bought a second hand bicycle for Rp 72000. After he repaired, he sold the bicycle.a) If the repairing cost is Rp. 24000, how much did Adi sell it to get Rp

15000 profit b) If Adi sold it for Rp 85000 and He got Rp 7500 loss How much did the repairing cost?

ANSWERa) Buying price : Rp 72000 Repairing Cost : Rp 24000 Profit : Rp 15000 Selling price ?

Selling Price = Buying Price + ProfitSelling Price = ( Buying price + Repairing cost ) + ProfitSelling Price = (Rp 72000 + Rp 24000 ) + Rp 15000Selling price = Rp 96000 + Rp 15000

Selling Price = Rp 111000

ANSWERb) Buying price : Rp 72000 Selling Price : Rp 85000 Loss : Rp 7500 Repairing Cost ?

Buying Price = Selling Price + Loss( Buying price + Repairing cost ) = Selling Price + Loss(Rp 72000 + Repairing Cost ) = Rp 85000 + Rp 7500Repairing Cost = Rp92500 - Rp 72000

Repairing Cost = Rp 20500

Do Exercise 28 page 43 no 2, 3, 4

Percentage profit & Percentage loss

Example ! Pg 44 no 1

Goods bought for Rp 72.000 and sold at Rp 90.000Find the percentage profit of the cost price !

Solution!Profit = Rp 90.000 – Rp 72.000

= Rp 18.000

% Profit = = 25%

*Smart Solution☺

If given, buying price and percentage of profit :

if given, buying price and percentage of loss :

Smart Solution☺ If given, selling price and percentage of profit :

if given, selling price and percentage of loss :

Example !

Arman buys a secondhand bicycle for Rp 350.000. Find the selling price, if Arman sold at a profit of 12 %!

DO EXERCISE 29 PAGE 44 NO 2, 3

Bruto, Netto and Tarra Bruto : the total weight ( the content and

the package ) Netto : the net weight ( only the content ) Tarra : the weight of package

In mathematics, we can write :

Bruto = Netto + TarraNetto = Bruto – Tarra Tarra = Bruto - Netto

Bruto / Total Weight Netto/ Net Weight Tarra

100kg 98,5 kg

50 kg 0,5 kg

33,7 kg 1,3 kg

Example 1 ! Pg 44 no 5

Bruto = Netto + TarraNetto = Bruto – Tarra Tarra = Bruto - Netto

1,5 kg49,5 kg

35 kg

Example 2 ! Pg 44 no 6 A retailer buys one

bag of cane sugar for Rp 120000. In bags are written : Total weight 100 kg Net weight 98 kg. This cane sugar sold for Rp 1400/ kg and ex-sugar bag sold for Rp 1500. How much will the store get profit from selling one bag?

Known : Buying price : Rp 120000Selling price :(98 kg x Rp 1400 ) + ex- sugar bagRp 137200 + Rp 1500Rp138700

Profit = Selling price – Buying price

= Rp 138700 – 120000

= Rp 18700

Discount / Rebate

• Discount also call rebate

• Rebate is usually used to

attract people’s interest.

• Rebate is usually express in percent (%).

Discount = marked price - sale price

Example ! At Kompas yesterday, there’s an

advertisement said that Gramedia at Grand Indonesia will give 30% discount for the BCA card holders. So, Ucup goes there to buy some books. If he buys 5 books for Rp. 150.000,00 and he pays with BCA cards, how much does he pay ? Actual Price = Rp. 150.000,00

Discount ( 30% x Rp. 150.000,00 ) = Rp. 45.000,00 -

Price after discount = Rp. 105.000,00

Principal - Interest

Types of Interest

interest which is calculated onthe original principal

Simple interest

interest which is calculated onthe amount of money at the endof each interest period(including interest)

Compound interest

Interest rate

Yearly or annually (per year or per annum)Semi annually or half-yearly (per a half year)Quarterly (per a quarter year or per 3 months)Monthly (per month)Weekly (per week)Daily (per day)

I R P

Total P I

Principal = Modal, Invest

Simple Interest ( Yearly )

Simple Interest ( Monthly )Where :I = Simple InterestP = PrincipalR = Interest Rate ( in %)t = time

Principal = Modal, Invest

Pardi invested his money in a bank Rp 15.000.000At rate of 18% per-annum. Calculate the simple interest Pardi received :a. at the end 1 yearb. at the end of 2 yearsc. After 7 yearsd. At the end of 8 months

Example 1! Pg 46 no 1

Given : Principal = Rp 15.000.000

Rate = 18% = 0, 18a) t = 1 year

I = P . R .tI = 15.000.000 x 0,18 x 1I = 2.700.000

So, Pardi received the simple interest for 1 year is Rp 2.700.000

Solution

Given : Principal = Rp 15.000.000Rate = 18% = 0,18

b. t = 2 yearsI = Rp 2.700.000 x 2I = Rp 5.400.000

c. t = 7 yearsI = Rp 2.700.000 x 7 I = Rp 18.900.000

d. t = 8 months

I = Rp 1.800.000

Principal( P )

Rate( R )

Time( t )

Simple Interest

( I )

The amount

at the end

200.000 5% Per-annum

2 years

1.500.000 2%Half yearly

One-half year

2 ½ % monthly

7 months 52.500

8%Per-annum

11 months 2.250.000

600.000 1 year 5 months

127.500

Copy this table into your book and fill the blank!

20.000 220.000

90.000 1.590.000

44.680,85 7819,15

2.096.273,29 153.726,71

15 %Per- annum 727.500

DO EXERCISE 30 PAGE 46 NO 1 - 4

GOD BLESS YOU ☺

Thank You For Your Attention