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Maths, Addmaths and Statistics: Post your doubts here!

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it very simple. like...
to make the direction diagrams you should apply the formula:
Va = Va/b + Vw

and for magnitudes you should use any formula u can, e.g. sin rule, cos rule and any formula which is applicable.
Thats it......?
 
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A small help ppl..
1. A barrel of oil when 2/5 full, weighs 12kg. When it is 1/4 full, its weight is 8kg. Find the weight of the empty barrel and its weight when the barrel is full.
2. By 12 noon a driver has completed 1/4 of a journey. By 2.30 p.m he has travelled 3/5 of it. If his speed is 56km/h, find the length of the whole journey.
Thank you.. :)
 
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A small help ppl..
1. A barrel of oil when 2/5 full, weighs 12kg. When it is 1/4 full, its weight is 8kg. Find the weight of the empty barrel and its weight when the barrel is full.
2. By 12 noon a driver has completed 1/4 of a journey. By 2.30 p.m he has travelled 3/5 of it. If his speed is 56km/h, find the length of the whole journey.
Thank you.. :)
Q1
lets first convert the fractions "1/4" and "2/5" to fractions with equal denominators.
denominator will be LCM of 4 and 5 i.e. 20
1/4 = 5/20
2/5 = 8/20

when barrel is filled "8/20 - 5-20" the wa]eight of water in it is "12-8" kg, right? becozthe figures "12" and "8" include the mass of barrel too (along with water) which is cancelled out when we subtract.
so, 3/20 filled barrel weighs 4 kg
we conclude 1/20 filled barrel weighs ummmm, lets do it by ratio and proportion method.
fraction of barrel filled : its weight
3/20 : 4
1/20 : x

x = 1.333

mass of empty barrel = mass of water filled barrel - mass of water
....................................= (lets take it as) mass of 1/4 (or 5/20) filled barrel - mass of water in it
....................................= 8 kg - (1.333 *4) ---------> [ 1.333*4 becoz we know mass of ONLY water in 1/20 filled barrel is 1.333 and that in 4/20 filled is 4*1.333)
= 8 - 5.332 = 2.668 (answer)

mass of fully filled barrel = 20 * 1.333 + 2.668

am i right?
 
Messages
3,401
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9,793
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523
A small help ppl..
1. A barrel of oil when 2/5 full, weighs 12kg. When it is 1/4 full, its weight is 8kg. Find the weight of the empty barrel and its weight when the barrel is full.
2. By 12 noon a driver has completed 1/4 of a journey. By 2.30 p.m he has travelled 3/5 of it. If his speed is 56km/h, find the length of the whole journey.
Thank you.. :)
Q2
we say, he completed "3/5 - 1/4 = 7/20" journey in "2 hrs 30 minutes, or simply, 2.5 hrs"
speed id 56 km/h

distance travelled in these 2.5 hrs = distance for 7/20 of his journey = speed * time = 56 * 2.5 = 140 km

ratio and proportion:-
fraction of total distance : distance
7/20 : 140
20/20 : x

x/140 = (20/20) / (7/20)
x/140 = 20/7
x = (20/7) * 140 = 400 km
 
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A small help ppl..
1. A barrel of oil when 2/5 full, weighs 12kg. When it is 1/4 full, its weight is 8kg. Find the weight of the empty barrel and its weight when the barrel is full.
2. By 12 noon a driver has completed 1/4 of a journey. By 2.30 p.m he has travelled 3/5 of it. If his speed is 56km/h, find the length of the whole journey.
Thank you.. :)
Q1
lets first convert the fractions "1/4" and "2/5" to fractions with equal denominators.
denominator will be LCM of 4 and 5 i.e. 20
1/4 = 5/20
2/5 = 8/20

when barrel is filled "8/20 - 5-20" the wa]eight of water in it is "12-8" kg, right? becozthe figures "12" and "8" include the mass of barrel too (along with water) which is cancelled out when we subtract.
so, 3/20 filled barrel weighs 4 kg
we conclude 1/20 filled barrel weighs ummmm, lets do it by ratio and proportion method.
fraction of barrel filled : its weight
3/20 : 4
1/20 : x

x = 1.333

mass of empty barrel = mass of water filled barrel - mass of water
....................................= (lets take it as) mass of 1/4 (or 5/20) filled barrel - mass of water in it
....................................= 8 kg - (1.333 *4) ---------> [ 1.333*4 becoz we know mass of ONLY water in 1/20 filled barrel is 1.333 and that in 4/20 filled is 4*1.333)
= 8 - 5.332 = 2.668 (answer)

mass of fully filled barrel = 20 * 1.333 + 2.668

am i right?
***amd***, I dont think so........


Mass of Barrel when its......
2/5 = 12kg
1/4 = 8kg

So by multiplying them to get same denominator we have

8/20 = 12kg
5/20 = 8kg

So in the mass difference is of 3/20 (as 8-5/20) Water weighted 4 k.g
So
1/20 = 1.3333333333333333333


So,
(i) Empty Barrel weights 12kg (I mean wieght of 8/20) - 8 * 1.3333333333 (I mean weight of 8/20 filling-Water) = 1.333333333333333333333333

CHECK : 1.333333 + (5*1.333333) = 8kg (5/20)
(i) Full Weights 1.3333333333 + (20*1.3333) = 28
right?
 
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Q2
we say, he completed "3/5 - 1/4 = 7/20" journey in "2 hrs 30 minutes, or simply, 2.5 hrs"
speed id 56 km/h

distance travelled in these 2.5 hrs = distance for 7/20 of his journey = speed * time = 56 * 2.5 = 140 km

ratio and proportion:-
fraction of total distance : distance
7/20 : 140
20/20 : x

x/140 = (20/20) / (7/20)
x/140 = 20/7
x = (20/7) * 140 = 400 km
Yup......... I think its fine :)
 
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***amd***, I dont think so........


Mass of Barrel when its......
2/5 = 12kg
1/4 = 8kg

So by multiplying them to get same denominator we have

8/20 = 12kg
5/20 = 8kg

So in the mass difference is of 3/20 (as 8-5/20) Water weighted 4 k.g
So
1/20 = 1.3333333333333333333


So,
(i) Empty Barrel weights 12kg (I mean wieght of 8/20) - 8 * 1.3333333333 (I mean weight of 8/20 filling-Water) = 1.333333333333333333333333

CHECK : 1.333333 + (5*1.333333) = 8kg (5/20)
(i) Full Weights 1.3333333333 + (20*1.3333) = 28
right?
empty barrel weighs 12 kg? o_O
 
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***amd***, I dont think so........


Mass of Barrel when its......
2/5 = 12kg
1/4 = 8kg

So by multiplying them to get same denominator we have

8/20 = 12kg
5/20 = 8kg

So in the mass difference is of 3/20 (as 8-5/20) Water weighted 4 k.g
So
1/20 = 1.3333333333333333333


So,
(i) Empty Barrel weights 12kg (I mean wieght of 8/20) - 8 * 1.3333333333 (I mean weight of 8/20 filling-Water) = 1.333333333333333333333333

CHECK : 1.333333 + (5*1.333333) = 8kg (5/20)
(i) Full Weights 1.3333333333 + (20*1.3333) = 28
right?
I didnt get this question. . Please if you could be a bit more clear.. Thank you..
 
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