SOLUTION: Could you please help me solve this problem? The circular blade on a saw has a diameter of 7.5 inches and rotates at 2400 revolutions per minute. Find the linear speed of the saw

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Question 1004806: Could you please help me solve this problem?
The circular blade on a saw has a diameter of 7.5 inches and rotates at 2400 revolutions per minute. Find the linear speed of the saw (in feet per second) as it contacts the wood.
So far I have tried multiplying the 7.5 inches and the 2400 rpm to get 18000 inches per minute, then dividing by 12 to turn inches into feet. Then I multiplied it by 60 to turn minutes into seconds. My answer was 90,000 feet per second, a different answer than what my book says.
Found 2 solutions by josmiceli, josgarithmetic:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The circumference is:
+C+=+pi%2Ad+
+d+=+7.5+ in
+C+=+7.5%2Api+
----------------
This is like a problem where string is
wrapped around the cicumference and
is unwound at a certain speed. How many
feet of string unwinds in one second?
-------------------
+7.5%2Api%2A2400+ inches of sawblade
passes by the wood in one minute
+18000%2Api+ in/min
--------------------
[ ft/sec ] = [ in/min ] x [ ft/in ] x [ min/sec ]
+18000%2Api%2A%28+1%2F12+%29%2A%28+1%2F60+%29+
+25%2Api+=+78.54+ ft/sec
Hope I got it

Answer by josgarithmetic(39838) About Me  (Show Source):
You can put this solution on YOUR website!
One revolution is 2%2Api%2A%287.5%29

2400%28rev%2Fminute%29%2A%28%282%2Api%2A%287.5%29%29%2F1%29%28inches%2Frev%29----------for inches per minute

---------for feet per second

%28%282400%2A2%2Api%2A%287.5%29%29%2F%2812%2A60%29%29%28feet%2Fsecond%29-------feet per second


Continue simplifying.
%28%2840%2A2%2Api%2A7.5%29%2F%2812%29%29

%2840%2Api%2A7.5%29%2F6

%2820%2Api%2A7.5%29%2F3

150%2Api%2F3

50pi---------feet per second