If both addends are round to greater number, will the estimate be greater than or less the the estimate number

Acollection of coins has value of 64 cents. there are two more nickels than dimes and three times as many pennies as dimes in this collection. how many of each kind of coin are in the collection?

The cost of using a service is $0.25 per min. what equation correctly represents the total cost c, in dollars, for d days of use?

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms