Qr Problem(s)

[mintz123]

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this seems so simple yet cant figure it out

A person travels to work at an avg speed of 40 mph, and returns home at 60 mph. Which of the following, in mph, is the avg speed for the entire trip? a. 45 b. 46 c. 48 d. 52 e. 54 Ans: C

avg speed = dist/time => 40 + 60 / 2 = 50 no?😕


Also, A painting which is 4 feet wide and 5 feet long is surrounded by a rectangular fram 6 inches wide. What percent of the area of the picture and the frame is occupied by the frame??

Area = (4)(5) = 20ft2
Frame Area= 4.5ft x 5.5ft = am i even doing this right?
6in x (1ft/12in)= .5ft

% = (Area of Pic. + Area of Frame)/ Area of frame x100 ??

 

[ddsbruin]

avg speed = total distance/time

you're travelling the same distance from point A to B, and B to A. (40+40)
the time from point A to B is one hour (40 mph). the time from point B to A is 40 miles at a rate of 60 mph. it takes 2/3 the time returning, thus a total time of (1+2/3).

48 = (40+40/1+2/3)

the picture frame is 6 inches wide, which adds 6 inches on each side for a total of 1 foot. with the frame, the area is 5x6=30. the picture is 4x5=20. 20 is 67% of 30. thus the frame is 33% of the total area.

if im wrong, let me know!

 

[Streetwolf]

As was stated above me, 40 and 60 are not distances, they are rates. You need to figure out the distances traveled based on those rates.

Also, this has been posted 2 billion times so search around if you still don't get it.

 

[ZenoVT]

Yea you know distance to and from work is the same so let x be the distance.

avg speed = total distance/ total time

total distance = 2x

total time = x/40 + x/60

2x / [x/40 + x/60] --> 2x [ 3x/120 + 2x/120 ] --> 2x / 5x / 120 -->
240x / 5x --> 240 / 5 = 48

 

[mintz123]

thx!! ill be sure to remeber this 👍👍