hey DUDE
greenhouse effect is a natural phenomenon which sustains our life by making the Earth warm and suitable for our life but it's also harmful due to pollution.
there are many greenhouse gases and one of them is carbondioxide. carbondioxide is released while burning fuels and other things and also released from cars, truck etc which causes air pollution. because of the increase of greenhouse gases (carbondioxide), more heat and radiations are being trapped and hence the temperature of Earth is rising abnormally.. and thus greenhouse effect is causing global warming. and we know how dangerous is global warming..
today we are facing so many problems and will face More in future if it's not controlled. seas and oceans are overflowing.. it's destroying polar habitats etc, many weak animals and plants are dying etc.
this way it's becoming harmful..
few ways to prevent this :-
◻ plant more and more trees since trees require carbondioxide to prepare their food by the process of photosynthesis i.e they will absorb more carbondioxide.
◻ walk or use bicycle to cover short distances.
◻ use public transport more instead of private vehicles if you are traveling alone.
◻ stop excessive use of non-biodegrable things.. and stop burning them.
◻ stop cutting trees.
Выразим длину линеек в сантиметрах: 220 м = 22 000 см
Подсчитаем, какая общая длина была бы у всех линеек, если бы они все были по 20 см.
20*1000=20 000 (см)
В условии же задачи сказано, что общая длина линеек 220 м или 22 000 см. Найдем разницу:
22 000 - 20 000 = 2000 (см) - эти "лишние" сантиметры имеют 30-сантиметровые линейки.
Узнаем, сколько их, разделив эту разницу на 10 см (30см-20см=10 см)
2000:10=200 - столько штук линеек по 30 см.
Осталось узнать, сколько линеек по 20 см:
1000 - 200 = 800 шт. линеек по 20 см.
ответ: 800 штук.