couple math questions!!!

[smile101]

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1) There are 3 consecutive even integers such that the 3rd of the 3 even integers is 10 more than the sum of the first and second. What is the third integer?
a. -8
b. -6
c. -4
d. -10
e. -2

I calculated it to be 12, which is obviously wrong!

2) The 5 tires that came with Steve's new car were rotated frequently so that each tire was used exactly the same amount of time as the others. The tires were replaced when the odometer read 24000 mi. For how many miles had each been used?
A. 30000
B. 24000
C. 18000
D. 20000
E. 19200

3) A river flows at 3 mi/hr. A man can row at 5 mi/hr in still water. If he rows 1 mi upstream and then floats back to the starting place, how many min will be required for the roundtrip?
A. 30
B. 42
C. 50
D. 60
E. 65

4) How do you calculate 85% of 3/8 without intensive time consuming calc....since the answers are in decimals???

What is relation between radian and revolution???

 

[Willem]

1) There are 3 consecutive even integers such that the 3rd of the 3 even integers is 10 more than the sum of the first and second. What is the third integer?
a. -8
b. -6
c. -4
d. -10
e. -2

I calculated it to be 12, which is obviously wrong!

If the smallest integer is x, then the value for 3 consecutive even integers is
x, x+2 and x+4
Now, we know the third number is 10 larger than the sum of the first two. So:
x+4 = 10 + x + x+2

Solving this, x=-8. This is our smallest number. They ask the third number which we said is x+4, or -4.

2) The 5 tires that came with Steve's new car were rotated frequently so that each tire was used exactly the same amount of time as the others. The tires were replaced when the odometer read 24000 mi. For how many miles had each been used?
A. 30000
B. 24000
C. 18000
D. 20000
E. 19200

Well, the car has gone 24000 miles, that is 4x24000 miles of tire wear in total, or 96000. Now, there is 5 tires in use and they all have equal wear, so 96000 dividied by 5 is 19200.

3) A river flows at 3 mi/hr. A man can row at 5 mi/hr in still water. If he rows 1 mi upstream and then floats back to the starting place, how many min will be required for the roundtrip?
A. 30
B. 42
C. 50
D. 60
E. 65

The man rows at 5 miles an hour and the river flows at 3 miles an hour. So he moves up the river at 2 miles an hour. This means he goes upriver 1 mile in 30 minutes. On the way back down river he does not row, he just lets his boat get carried in the 3 mile an hour current. At 3 miles an hour it will take him 20 minutes to return back to the starting point.

4) How do you calculate 85% of 3/8 without intensive time consuming calc....since the answers are in decimals???

You can estimate I suppose. Someone correct me if im wrong but I dont believe there is a "quick" way to this answer and most likely a guess is all you will be able to do if speed really is an issue. 3/8 is 0.375. So, 85% of it cannot be any higher than that. 90% of it is sort of easy to do in your head, just take 0.0375 away from 0.3750 and get 0.3375. You know its got to be less than this. To get 80% of that you can take away that 0.0375 again which gives you 0.300. So its got to be higher than this value and lower than the 90% mark. If you cant do this in your head quickly(I dont imagine many can) you will be best served by just writing out the multiplication on paper. .375 times .85. Simple. The only thing you need to remember is where the decimal goes in case youve forgotten over time. Writing it out will not take long.

 

[smile101]

hey....thanks a bunch...this helps, especially the cool trick on 85% problem!!!

 

[ak47]

1 revolution = 2(pi) radians = 360 degrees