In every five people, one is 75 years old or above
The ratio of people who are 75 years old and above is 1:5
*In every five people, one is 75 years old or above. - This means that it is possible that in a group of 5 people amongst them one is 75 years.
*The ratio of people who are 75 years old and above is 1:5- Ratio means proportion. It is usually used to refer to probability.
1:5 read as one is to five.
*In every five people, one is 75 years old or above.
５人に１人は７５歳以上です。
５人中の１人は７５歳だという可能性を表しています。
*The ratio of people who are 75 years old and above is 1:5
７５歳以上の人口割合は1:5です。
ratioとは割合という意味です。通常、確率を表します。
1:5はone is to fiveと読みます。
Eighty percent of people are under 75 years of age.
You may either describe the number of older people whose age is past the threshold of 75 as being 'twenty percent,' or, as a statistic of age distribution for a country, you could refer to the 'eighty percent' of people who are under 75.
"My grandfather is one of the twenty percent of pensioners aged over 75."
75歳を過ぎた高齢者の数が "twenty percent"(20%)であるまたは、その国の年齢分布を考えて、75歳以下の人が"eighty percent"(80%)であるということもできます。
"My grandfather is one of the twenty percent of pensioners aged over 75."
（私のおじいちゃんは20%いる75歳以上の年金受給者のひとりです。）
These sentences give different examples of how you can say '1 in 5'. It is common in English to just say an age as '75' or whatever the number is, without adding 'years' or 'years old'.
The terms 'over', 'or older' and 'or over' all describe that the age includes 75 years and then goes above this as well. Therefore, they are not just 75 and they are not younger than 75.
One in five people are 75 years old or older in Japan.
One in five' or 'one-fifth' is the correct way to say this amount. It is also important to clarify which population you are referring to unless it is already very obvious from the previous conversation.
One in five'（5分の1）または 'One-fifth'（同）がこの数量の正しい言い方です。
また、それまでの会話で明白になっている場合を除いて、どこの人口について言っているのか明確にすることも重要です。
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