R1SI3r42jhkfA

Calculating the percentage of the number

Source: licencja: CC 0.

Obliczanie procentu danej liczby

Learning objectives

You will discover the method of calculating the amount after reduction or increase by a given percentage.

Learning effect

  • You calculate the percentage of a given number.

  • You calculate the price of the product after the reduction or the increase by a given percentage.

  • You calculate the amount of the salary after the increase by a given percentage.

  • You use English to describe the percentage of the given number.

Prepare for the lesson the following items:

RAQoI15l8rwEz1
nagranie abstraktu
  • 10 self‑adhesive cards with the inscriptions of: 1% of 400, 1% of 3,000, 10% of 300, 10% of 400, 25% of 16, 25% of 40, 25% of 120, 50% of 60, 50% of 800, 100% of 40,

  • 5 sheets of A‑4 size. Write one of the following numbers : 4, 10, 30, 40, 400 on each of them.

Revise the notion of percentagepercentagepercentage and the method of calculating the fraction of the number.

Answer the following questions:

  • What is the percentage?

  • How can we convert the percentage in the fraction?

  • How the fraction of the number is calculated?

Revision:

R1FNDACcM9bex1
nagranie abstraktu
  • One percent of the certain amount is the one hundredthone hundredthone hundredth of it, what is written as the following:

1%a=1100a=0,01a
  • Converting the percent in the fraction we divide the fraction by 100%.

  • Converting the fraction in the percentagepercentagepercentage we multiply the fraction by 100%.

R1ciIomOFADra1
nagranie abstraktu

Today you are going to calculate the percentage of the given amount. You are also going to calculate the pricepriceprice of the products after the reductionreductionreduction by a given percentage and the amount of the salary after an increaseincreaseincrease by a given percentage.

Consider:How can we calculate the percentage of given number?

Notice, that:

  • To calculate the percentage of the number we convert the percentagepercentagepercentage in the common or decimal fractioncommon fractiondecimal fraction and then, we multiply the fraction by the number.

Task 1
Roo536uTLz1Pu1
nagranie abstraktu

Put the cards with the numbers: 4, 10, 30, 40, 400 in front of you. Choose the self‑adhesive stickers and stick them on the sheets with the answers.

Task 2

Calculate:

a) 15% of 80
b) 24% of 300
c) 3% of 7
d) 68% of 25
e) 91% of 50

RhYgNluabVBbd1
nagranie abstraktu

The slideshow concerns the information about the prices in the shop. After watching it complete the task 3 and 4.

RrAzU3OjuKEf71
Prezentacja multimedialna przedstawia ceny aparatu fotograficznego, telewizora, roweru, pralki i laptopa. Instrukcja obsługi z poziomu klawiatury: 1. Uruchomienie aplikacji - ENTER, 2. Na każdym ze slajdów czytany jest automatycznie tekst alternatywny po polsku, 3. Przy pierwszym uruchomieniu na pierwszym slajdzie, czytanie tekstu po angielsku - TAB, 4. Przejście między slajdami: do następnego slajdu - TAB, do poprzedniego slajdu - TAB + SHIFT, 5. Przejście do czytania napisu po angielsku - strzałka w górę + strzałka w dół (czyta tekst po angielsku widoczny na slajdzie).
Source: GroMar, licencja: CC BY 3.0.
Task 3
R1FgYiKgem4Wb1
nagranie abstraktu

Calculate how much money we pay for the camera, the TV, and the bike, knowing that:

a) the pricepriceprice of the camera was reduced by 20%,
b) the price of the TV was reduced by 30%,
c) the price of the bike was reduced by 45%.

Task 4
RyKkjErYBqWQn
nagranie abstraktu

Calculate the prices of the camera, the TV and the bike after the reductionreductionreduction.

RuE8eecGDPqaA
nagranie abstraktu

Sum up the activities in task 3 and 4 looking for the answers to the following question:

  • How can we calculate the price of the product after the reduction by a given percentagepercentagepercentage?

R1UMxeI6icCpb
nagranie abstraktu

Notice, that:

  • first, we calculate the amount of the reduction, so we calculate the percentage of the pricepriceprice,

  • next, we subtract the amount of the reduction from the initial price.

R1WAKYp5id0fr1
nagranie abstraktu

Watch the slideshow concerning the amount of the salary of three people and complete the tasks 5 and 6.

R1II6aUa20kBU1
Pokaz multimedialny - wysokość wynagrodzenia. Instrukcja obsługi z poziomu klawiatury: 1. Uruchomienie aplikacji - ENTER, 2. Na każdym ze slajdów czytany jest automatycznie tekst alternatywny po polsku, 3. Przy pierwszym uruchomieniu na pierwszym slajdzie, czytanie tekstu po angielsku - TAB, 4. Przejście między slajdami: do następnego slajdu - TAB, do poprzedniego slajdu - TAB + SHIFT, 5. Przejście do czytania napisu po angielsku - strzałka w górę + strzałka w dół (czyta tekst po angielsku widoczny na slajdzie).
Source: GroMar, licencja: CC BY 3.0.
Task 5
R1Ph1RhotVGbP1
nagranie abstraktu

Calculate how much more money after the increaseincreaseincrease Darek, Paul and Adam get knowing that:

a) Darek’s earningsearningsearnings increased by 12%,
b) Paul’s earnings increased by 4%,
c) Adam’s earnings increased by 19%.

Task 6
RMda3Rr3WqPUK
nagranie abstraktu

Calculate the amount of the salary of Darek, Paul and Adam after the increase.

Rxs59590BzWZB
nagranie abstraktu

Sum up the activities in the task 5 and 6 by answering the question:

  • How can we calculate the amount of the earningsearningsearnings after the increase by a given percentage?

R4BpAKKf8zdon
nagranie abstraktu

Notice, that:

  • we calculate the amount of the increase , so we calculate the percentage of the number for the amount of the salary,

  • next, we add the amount of the increase to the initial amount of the salary.

Task 7

An extra task:

Find out in the literature or on the Internet the other method of calculating the reductionreductionreduction and the increaseincreaseincrease of the specified amount by a given percentage.

Remember:

Rpsv9mpm9npot1
nagranie abstraktu
  • To calculate the percentagepercentagepercentage of the number we convert the percentage in the common or decimal fractiondecimal fractiondecimal fraction and then, we multiply the fraction by the number.

  • To calculate the reductionreductionreduction by a given percentage we calculate the percentage of this amount and we subtract the result from the initial number.

  • To calculate the increaseincreaseincrease by a given percentage we calculate the percentage of this amount and we add the result to the initial number.

Do the summarizing tasks.

Exercises

R8J4nozdm0hPS
Exercise 1
Wersja alternatywna ćwiczenia: Determine which sentences are true. Możliwe odpowiedzi: 1. 20% of 45 minutes = 9 minutes, 2. 10% of 80 km = 8000 m, 3. 8% of 1 metre = 8 cm, 4. 25% of 1 hour = 20 minutes, 5. 33% of 1 decimetre = 3 cm, 6. 20% of 1 tonne = 20 kg, 7. 4% of 500 g = 20 g
zadanie
Source: GroMar, licencja: CC BY 3.0.
Exercise 2

The skis have cost 2300 PLN. Their price was reduced by 20% first, then the price was increased by 20%. What is the price of the skis now?

Exercise 3

Calculate:

a) 32% of  90

b) 2% of 4500

Describe the method of calculating the percentage of the number in English.

RieLOZxULtQpa
Exercise 4
Wersja alternatywna ćwiczenia: Indicate which pairs of expressions or words are translated correctly. Możliwe odpowiedzi: 1. procent - percentage, 2. obliczanie procentu danej liczby - reduction of the percentage of the number, 3. obniżka - reduction, 4. podwyżka - increase, 5. cena - earnings, 6. ułamek zwykły - decimal fraction
zadanie
Source: GroMar, licencja: CC BY 3.0.
R11XfNnJBjEGf1
Interaktywna gra, polegająca na łączeniu wyrazów w pary w ciągu jednej minuty. Czas zaczyna upływać wraz z rozpoczęciem gry. Jeden ruch to odkrywanie najpierw jednej potem drugiej karty z wyrazem. Każdy wyraz jest odczytywany. Kolejny ruch to odkrywanie trzeciej i czwartej karty. W ten sposób odsłuchasz wszystkie wyrazy. Nawigacja z poziomu klawiatury za pomocą strzałek, odsłuchiwanie wyrazów enterem lub spacją. Znajdź wszystkie pary wyrazów.
Source: Zespół autorski Politechniki Łódzkiej, licencja: CC BY 3.0.

Glossary

percentage
percentage

procent

RUazGaTdqWFQe1
wymowa w języku angielskim: percentage
reduction of the percentage of the number
reduction of the percentage of the number

obliczanie procentu danej liczby

RyFeSnRI5L3NI1
wymowa w języku angielskim: reduction of the percentage of the number
reduction
reduction

obniżka

Rlcj68HiDY1Ov1
wymowa w języku angielskim: reduction
increase
increase

podwyżka

R1EhXH3izFvZO1
wymowa w języku angielskim: increase
price
price

cena

Ra4iuqqRUgzLs1
wymowa w języku angielskim: price
common fraction
common fraction

ułamek zwykły

R1Qf7Cav6mfih1
wymowa w języku angielskim: common fraction
decimal fraction
decimal fraction

ułamek dziesiętny

RjhaIGLTT6lrE1
wymowa w języku angielskim: decimal fraction
one hundredth
one hundredth

jedna setna

R18K5wRd3GUCz1
wymowa w języku angielskim: one hundredth
earnings
earnings

wynagrodzenie

RtRfDM3bs80ER1
wymowa w języku angielskim: earnings

Keywords

percentagepercentagepercentage

reduction of the percentage of the numberreduction of the percentage of the numberreduction of the percentage of the number

reductionreductionreduction

increaseincreaseincrease

pricepriceprice