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Mathematics 6.

Table of contents
Calculating the rate
(\latex{ 26.3}%)
SZEGED
VESZPRÉM
-
-
:
\latex{ 28 }
\latex{ 25 }
\latex{ 25 /54}
\latex{ 28 /47}
\latex{ 3 /4}
\latex{ 2 /3}
\latex{ 10 /38}
\latex{ 13 /38}
(\latex{ 34.2}%)
(\latex{ 75}%)
BLOCKS / SHOTS
(\latex{ 46.3}%)
(\latex{ 66.7}%)
(\latex{ 59.6}%)
MEN´S HANDBALL CHANPIONSHIP
GOALS / SHOT
\latex{ 7 }M / SHOTS
Example 1
In minute \latex{ 25 }, Szeged was leading against Veszprém \latex{ 15:12 }. Szeged needed \latex{ 20 } shots to score \latex{ 15 } goals. What is their efficiency %\latex{?}
Solution 1
\latex{ 20 }      shots
\latex{ 15 }      goals
\latex{ 100 }%
?
\latex{20}
\latex{100}
shots
\latex{ 1 }%
\latex{\qquad 15 \quad}   goals     \latex{ \qquad\qquad\qquad15\div\frac{20}{100}}% \latex{=15\times\frac{\overset{5}{\cancel{100}}}{\underset{1}{\cancel{20}}}}% \latex{=75}%
Solution 2
\latex{\qquad 20 \qquad} shots\latex{ \qquad\qquad\qquad\qquad100 }%
\latex{\qquad1\qquad}   shot   \latex{ \qquad\qquad\qquad\qquad\frac{100}{20}}% \latex{ =5 }%
\latex{\qquad 15 \qquad} goals\latex{ \qquad\qquad\qquad\qquad15\times5 }% \latex{ =75 }%
Solution 3
\latex{ 1 } shot is \latex{\frac{1}{20}} of \latex{ 20 } shots,
\latex{ 15 } goals are \latex{\qquad\frac{15}{20}} of \latex{ 20 }.
\latex{\frac{15}{20}=\frac{75}{100}\rightarrow75} %.
Until minute \latex{25}, the efficiency of Szeged was \latex{75}%.
Example 2
Last \latex{ year, } there were \latex{ 30 } athletes at a school. This \latex{ year }, there are \latex{ 42 }. What percentage of last \latex{ year's } number of athletes is the current number of athletes?
Solution 1
Last \latex{ year's } number of athletes should be \latex{ 100 }%.
\latex{ 30 }      athletes
\latex{ 42 }      athletes
\latex{ 100 }%
?
\latex{1} athlete
\latex{ 100 }
\latex{ 30 }
%
                 \latex{\qquad 42 \quad} athletes   \latex{ \qquad\qquad\qquad\overset{7}{\cancel{42}}\times\frac{{100}}{\underset{5}{\cancel{30}}}}% \latex{=\frac{700}{5}}% \latex{=140}%
Solution 2
\latex{ 42 } athletes are \latex{\frac{42}{30}} times \latex{ 30 } athletes.
 
\latex{\frac{42}{30}=\frac{7}{5}=1.4.}   \latex{ 1.4 } \latex{\rightarrow140}%.
This \latex{ year's } number of athletes is \latex{ 140 }% of last \latex{ year's } number of athletes.
The number of athletes has increased by \latex{ 40 }%.
Example 3
At a store, there is a \latex{ 25 }% discount on a juice; at another, there is a 'buy two, get one free' offer for the same juice. In which store should you buy the juice?
Solution 1
At the first store, the discount is \latex{ 25 }%.
At the other store, you can get three boxes of juice for the price of two.
\latex{ 3 } boxes of juice                           \latex{ 100 }%
\latex{ 1 } box of juice                               \latex{\frac{100}{3} }%
\latex{ 2 } boxes of juice                           \latex{2\times\frac{100}{3}}% \latex{=66.\dot{6}}% \latex{ \approx 66.7}%
Thus, the discount is \latex{ 100 }%\latex{ - 66.7 }% \latex{ = 33.3 }%.
Solution 2
If you can get \latex{ 3 } boxes of juice for the price of \latex{ 2 }, then one box costs \latex{\frac{2}{3}} of the price of \latex{ 2 } boxes.

\latex{\frac{2}{3}=0.66\dot6 \approx 0.667.\quad 0.667} \latex{\rightarrow 66.7 }%.   The discount is \latex{ 33.3 }%.
 
It is worth buying the juice at the second store.
Exercises
{{exercise_number}}. Conduct a survey in your class and make a table.
What % of the students in your class
  1. wear glasses;
  1. have been abroad;
  1. went to the zoo last year;
  1. take the bus to school?
{{exercise_number}}. Conduct a survey in your class and make a table.
  1. What % of the students got an \latex{ A }, a \latex{ B }, a \latex{ C }, a \latex{ D }, and an \latex{ F } on the last maths test?
  2. What percentage of the students in your class have \latex{0}; \latex{1}; \latex{2}; \latex{3} or more than \latex{ 3 } siblings?
{{exercise_number}}. Think of similar questions as in exercises \latex{ 1 } and \latex{ 2 }, and conduct a survey.
{{exercise_number}}. What % of \latex{ 50 } are the following numbers?
  1. \latex{1}
  1. \latex{2}
  1. \latex{5}
  1. \latex{22}
  1. \latex{65}
  1. \latex{150}
{{exercise_number}}. What percentage of \latex{ 1 \;hour } is
  1. \latex{60\,minutes};
  1. \latex{15 \,minutes};
  1. \latex{75 \,minutes};
  1. \latex{6 \,minutes};
  1. \latex{3 \,minutes};
  1. \latex{90 \,minutes?}
{{exercise_number}}. What percentage of \latex{ 2 \,km } is
  1. \latex{800 \,m};
  1. \latex{240\,m};
  1. \latex{1,625 \,m};
  1. \latex{2.3\,km};
  1. \latex{20 \,m};
  1. \latex{80 \,m?}
{{exercise_number}}. The price of a €\latex{ 25 } dress was increased by €\latex{ 5 }. What percentage of the original price is the new price?
{{exercise_number}}. The price of a €\latex{ 30 } item was reduced by €\latex{ 18 }. What percentage of the original price is the new price?
{{exercise_number}}. \latex{ 2,430 } of the \latex{ 45,000 } books in a library are in a foreign language. What percentage of the books in the library are in a foreign language?
{{exercise_number}}. At a shooting gallery, \latex{ 15 } of \latex{ 36 } shots hit the target. What percentage of the shots hit the target?
{{exercise_number}}. The diagram shows the results of a survey conducted among sixth-graders on how many smart devices they have. What percentage of the students have \latex{ 1 }, \latex{ 2 }, and \latex{ 3 } smart devices?
\latex{ 42 } students
\latex{ 12 }
students
\latex{ 6 }
\latex{ 1 } device
\latex{ 3 } devices
\latex{ 2 } devices
students
{{exercise_number}}. A car travelled \latex{ 168 \;km } of a \latex{ 250 \;km } long journey. What percentage of the journey is completed?
{{exercise_number}}. A pen costs \latex{ 50 \;cents, } while a pencil costs \latex{ 40 \;cents }. What percentage of
  1. the pen's price is the price of a pencil;
  2. the pencil's price is the price of a pen;
  3. the sum of a pencil's and a pen's price is the price of a pen;
  4. the sum of a pencil's and a pen's price is the price of a pencil?
{{exercise_number}}. A family's monthly income is €\latex{ 2,600 }. They spend €\latex{ 350 } on bills (gas, electricity, water, telephone, Internet, newspapers), €\latex{ 450 } on food and household items, and €\latex{ 110 } on transport and other expenses. What percentage of the monthly income is spent on each type of expense?
{{exercise_number}}. Ask your parents what percentage of your income is spent on bills and food. What percentage of your income do you spend on leisure?
{{exercise_number}}. The table shows the number of students from each grade participating in a maths competition.
grade
number of students
\latex{ 3rd }
\latex{ 4th }
\latex{ 5th }
\latex{ 6th }
\latex{ 7th }
\latex{ 8th }
\latex{ 9 }
\latex{ 15 }
\latex{ 33 }
\latex{ 27 }
\latex{ 24 }
\latex{ 12 }
What percentage of the students were third, fourth, fifth, ..., eighth-graders?
{{exercise_number}}. By what percentage did the store reduce the price of each winter sportswear item?
\latex{ \text{\textemdash} }
€\latex{ 60 }
€\latex{ 6 }
€\latex{ 80 }
€\latex{ 12 }
€\latex{51 }
\latex{ \text{\textemdash} }
\latex{ \text{\textemdash} }
\latex{ \text{\textemdash} }
\latex{ \text{\textemdash} }
€8
€\latex{ 6 }
€\latex{ 9 }
€\latex{ 72 }
€\latex{3 }
Quiz
Crisis in the New Village sports club.
The local newspaper tried to find out what caused the poor performance of the local NVS football team.
– I think the criticism we got is just unfair. Our performance in the second half of the season improved by
\latex{ 100 }% – said the coach.
– The NVS has never performed so poorly. We only won \latex{ 3 } of our \latex{ 30 } games –complained a fan.
They both told the truth. How is this possible?