math question! I've been working on this, but can't seem to get it right. need help solving!
Uh-Huh
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Friday, 6th of August 2010 05:05:23 AM
The county is new asphalt paving machine can surface 1 km of highway in 10 Uh-Huh hours. A much older machine can surface 1 km in 18 hours. How long will it Registered User take them to surface 21 km of highway if they start at opposite ends and Joined: Wednesday, 19th of May 2010, 11:31:08 work day and night?
if you can show me the process of how to Posts: 1430 solve this, so l can learn how to do this, that would be awesome. :)
Viewed 14794 times
quiero
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Saturday, 7th of August 2010 08:13:25 AM
Machine A: 1km in10hours > 1/10kms in 1hour quiero Machine B: 1km in18hours > 1/18kms in1hour Registered User ----------------------- Joined: Thursday, 27th of May 2010, 16:31:52 Together they do 1/10+1/18 kms in 1 hour=14/90 kms in 1 hour Posts: 1421 ----------------------- Viewed 5716 times 14/90 kms * x hours=1km > x=90/14 hours for 1 km
-------------------------
Then for 21 kms---> 21kms*(90/14)(hrs/1km)=135 hours
I think that is understandable and i hope this could help you.
BLACK CAT
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Sunday, 8th of August 2010 06:36:10 AM
New Asphalt Paving Machine: BLACK CAT Registered User For every 10 hr, 1 km is paved Joined: Sunday, 16th of May 2010, 17:59:27 Posts: 1928 Old Asphalt Pavingt Machine: Viewed 10569 times
For every 18 hr, 1 km is paved.
Find: How many hours it will take them to pave 21 km?
Solution:
Let h number of hours to pave 21 km together.
(1km/10hr)(h) + (1km/18)(h) = 21 km
h/10 + h/18 = 21
18h + 10h = 21(180)
28h = 3780
h = 3780/28
h = 135 h ANS
Hope I help you.
teddy boy
Mr. Mean Jeans
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Monday, 9th of August 2010 07:43:57 PM
Okay, first you have to find the actual speeds of both Mr. Mean Jeans machines. Registered User Joined: Saturday, 22nd of May 2010, 20:11:33 The new machine does 1 km in 10 hrs, that is 1/10 per hour or .1 km/hr. Posts: 414 The old machine does 1 km in 18 hrs, which is 1/18 per hour, or .05555/hr. Viewed 2907 times (I am rounding off. It is actually 1.55555555, etc etc.)
Add them together you get .15555 km. per hr. for both of them working
together.
So now you want to do 21 km of highway. At .1555 per hour you divide 21
km by .15555 & get 135.004 hrs. Working day & night this is 135.004/24,
which equals 5.625 days. Or five days & 5 days & 15.004 hrs.
(And since we're already rounding off, you could just say 5 days & 15 hrs.
That .004 hrs is just 14.4 seconds.)
NoteZ
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Tuesday, 10th of August 2010 11:26:08 PM
old = 1km/10hrs = 0.1km/hr NoteZ new = 1km/18hrs = 0.0555556 km/hr Registered User add to get combined rate of 0.1555556 km/hr Joined: Thursday, 3rd of June 2010, 11:16:38 Posts: 933 21km at 0.1555556 km/hr = Viewed 18589 times 21/0.1555556 = 135 hours
Jumboshrimp ;]
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Wednesday, 11th of August 2010 01:05:58 AM
time for 1 km = (A x B) / (A + B) Jumboshrimp ;] Registered User A = 10h Joined: Thursday, 3rd of June 2010, 21:07:21 B = 18h Posts: 2034 Viewed 1327 times (10*18)/(10+18) = 180/28
for 21km: (180/28)(21) = 135hrs
this is the shortcut method. i can explain it in full, but the full-length
way is just too complicated for something like this.
Crazy Legs
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Thursday, 12th of August 2010 03:39:30 AM
How much can each do in 1 hour? Crazy Legs Registered User (1/10) km + (1/18) km. At that rate, how long will it take them to do the Joined: Wednesday, 28th of April 2010, 22:49:55 whole 21 km? Posts: 1790 Viewed 5617 times 21/(1/10+1/18) hours
Fluffy-kun
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Friday, 13th of August 2010 08:42:59 PM
i am doing he same exact thing.almost i need to know this too Fluffy-kun Registered User Joined: Friday, 7th of May 2010, 02:29:27 Posts: 864 Viewed 6182 times
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