What percentage of numbers from 1 to 70 has 1or 9 in their number digit

20% of number 1 to 70 has one or nine in it

Explanation:

20% numbers from 1 to 70 have 1 or 9 in the unit's digit. 1,9,11,19,21,29,31,39,41,49,51,59,61,69 this is that series of numbers .These are total 14 numbers out of 70 so 14/70×100 gives us 20 % occurrence of 1 or 9 at unit place.

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developed countries have tended to improve the environment, while developing countries have tended to damage it.