三時間も・ 十万円はas many as; at least
After a number, も and は say how the number strikes you. も: that is a lot. は: that much at the least, and maybe more.
a lot
I thought this job would take an hour, but it took a full three hours.
at least
If you want to buy this computer, you'll need at least 100,000 yen.
How to form it
Number + counter + も/は
Straight after the amount: a time, a price, a distance, a count.
One number, three ways
It takes a whole thirty minutes to walk to the station.
That is a lot.
Walking to the station takes at least thirty minutes.
No less than that, and maybe more.
It only takes thirty minutes to walk to the station.
That is not much. With しか the verb turns negative.
も: that many
The amount is more than you expected, and you are surprised, impressed or fed up. It only has to be a lot for the situation: three cakes are a lot for one person.
He ate three cakes all by himself.
This notebook cost five thousand yen?
English often has no word for this も. It leans on the number.
It's only a small shop, but thirty people were lined up before it even opened.
With 何 in place of the number it means "many": 何回も, "many times"; 何年も, "for years".
I called many times, but nobody answered.
は: at least that many
You are estimating, and this is the floor: it won't be less. It is common with かかる, 必要だ and でしょう.
The repair will probably take at least a week.
This hall can hold at least a hundred people.
I'd like to climb Mt. Fuji at least once.
一度は is "at least once".
一人も, 一度も: not even one
With a negative verb, 一人も, 一つも and 一度も are "not even one": nobody, nothing, never.
There isn't a single student in the classroom.
I have never once been to Kyoto.
Close neighbours
三人しか~ないN4
The opposite of も: "only" that many, fewer than you wanted. The verb is always negative.
We needed ten people for the meeting, but only three came.
以上N4
For a rule or a limit: exactly that number or more. は is a rough floor in an estimate.
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Check yourself
1What does this mean?
昨日は
Choose an answer to see why.
2What does this mean?
空
Choose an answer to see why.
3Which one fits?
今日は
Choose an answer to see why.
More detail
With a negative verb, は is often "less than": 駅まで十分はかかりません, "it takes less than ten minutes to get to the station".
Before あれば, も is a generous guess at what will be enough: 十分もあれば着きます, "ten minutes is plenty to get there".
少なくとも, "at least", often comes in front of the は kind: 少なくとも三日はかかります, "it will take three days at the very least".
More sentences
I called twenty times before I got a reservation.
She read a hundred pages of this book in one day.
We walked a full ten kilometers from the station to the coast.
There are as many as two hundred photographs in this small box.
We will need at least twenty cardboard boxes for the move.
You need at least three hours to read this book.
I spend at least 10,000 yen on transportation every month.