Question Video: Calculating Times and Dates That Are 12 Hours Later Mathematics

A business woman went to her company on Wednesday morning at the time shown. She had a lot of work, and it took her 12 hours to finish it. At what time did she finish?

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Video Transcript

A business woman went to her company on Wednesday morning at the time shown below. She had a lot of work, and it took her 12 hours to finish it. At what time did she finish?

And we can see that we’ve got four different answers to choose from here. Let’s go through the question carefully and try to pick out the important information. To begin with, we’re told that a business woman went to her company on Wednesday morning. This is important because three of our answers show times on Wednesday, and one shows a time on Thursday. So, the day and the time of day are important here. But we’re also given more information than this. We’re told the exact time that this lady goes to her company. It’s the time on the clock.

What time did she go to work? The minute hand on this clock face is pointing to the six. It’s gone half the way around the clock face, and so we know it’s a half past time. The hour hand is halfway between the number eight and nine. And so, we know it’s half the way past 8 o’clock on its way to 9 o’clock. The time is half past 8. So, we’re told that this lady goes to work at half past 8 in the morning.

We’re then told that she had a lot of work to do, and it took her 12 hours to finish it. That’s quite a long workday. Now, this amount of time, 12 hours, is important. What do we know about 12 hours? We know that 12 hours is the length of time it takes for the hour hand to start from a position on the clock face and go all the way around back to where it started. And we can use this fact to help us. As we’ve said already at half past 8 in the morning, the hour hand is halfway between the number eight and nine. And so, 12 hours later, when this lady finishes her work, it’s going to be halfway between the eight and the nine again. The time will be half past 8 again.

If we look at our first possible answer, we can see that the clock shows half past 8 on Wednesday. And if we look at the window, we can see the sun is up in the sky. It looks like it’s Wednesday morning, doesn’t it? This lady doesn’t finish her work on Wednesday morning at half past 8; this is when she starts work. So this isn’t the right answer. But you know, we’ve got another morning time in our answers too. This one shows Thursday morning at half past 8. Now, if it only took 12 hours to get from Wednesday morning at half past 8 to Thursday morning at half past 8, then we could say that there are 12 hours in a day, but we know there are 24 hours in a day. So if this lady was to finish our work at half past 8 in the morning the next day, that would mean she’d spent 24 hours on it, not 12.

So, we’re left with two possible answers. We know that we’re looking for a half past 8 time. And both of these pictures show Wednesday night. We can see that because the moon’s out in the sky. Now, which one of our clocks shows half past 8? It’s this one, isn’t it? The minute hand is pointing to the six, and the hour hand is halfway between the eight and the nine. Let’s not make the mistake of choosing this answer. If you look at this clock, we can see that the minute and the hour hand have been swapped around. We don’t wanna get them muddled up, do we? The time that is 12 hours later from Wednesday morning at half past 8 is Wednesday evening at half past 8.

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