Thursday, March 11, 2010

Michelle Obama's Plane

Michelle Obama was returning from LA on a 747 and her White House Chief of Security planned to pick her at the airport in a special bulletproof car. Obama's plane landed ahead of schedule and the security chief unaware of it was still on his way. Michelle took a congressman's limousine back home. Fifteen minutes later security chief car intercepted the limousine on the way and asked the First Lady to switch cars. She was so happy to be back at the White House twenty minutes earlier than scheduled. When Washington chief of security had to file a day progress report, he was at loss as to when exactly the plane landed. The original schedule stated landing at 3.30pm. Can you help him?

This is a fictional story. The puzzle is adopted from the book by B. Kordemsky

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Anonymous said...

Ask the pilot, or the tower. Tom

Maria said...

They may reveal to the news hungry media that White House Chief of Security did not know it. Can he use some math to figure this out?

Anonymous said...

Assuming she did not lose time waiting for her Chief of security at the airport first or while changing cars, you say that she arrived 20 mts earlier at the White House. So the plan must have arrived 20 mts earlier than scheduled, at 3:10 PM.

Maria said...

My fault. I forgot to mention that the White House bulletproof car may be driving with a much faster speed than a congressman's limousine. The first one is surrounded by police motorcycles and doesn't stop on red right.

So, we compare here a planned plane arrival at 3.30pm plus a ride in a White House car
with an
early arrival plus15 minute slow limousine ride plus remaining ride in a White House car plus extra 20 minutes.

It is simple yet tricky puzzle.
A clue: think how many minutes away from the airport was the White House Security Chief when plane landed?

Anfisa said...

Obama's plane was scheduled to arrive at 3:30pm and the bulletproof car was scheduled to arrive at airport at 3:30pm. Instead, the bulletproof car met Mrs Obama 15 mins earlier on the road. Mrs Obama had already landed 15 mins earlier. Therefore, the bullet proof car was 30mins away when the plane landed. If he was on schedule to meet the plane, the plane must of landed at 3:00pm.

Maria said...

Anfisa, you are almost there!
You didn't use 20 min early arrival...
I added a chart above that should help.

Anonymous said...

Well, I had to do math. But I did not think that I needed to do it because "it is fictional story".
I operated with speed of both cars that are b (bulletproof) and l (limousine). I found out distance from airport for bulletproof car when plane landed with 2 formulas: "b *(3:30pm - actual time) and 15b + 15l". Then I had to use 20 mins somehow. I know that scheduled arrival to White House is 3:30pm + distance/b. I know that actual arrival to White House that happened 20 mins earlier is "actual time of plane arrival + (distance - 15l)/b + 15".
I calculated actual time as 3:05pm.
I am wondering though if I could just go with fictional story. Although, when speed is involved, math picks up.

Anfisa said...

Above is post from Anfisa

Maria said...

Wow! You did it, Anfisa!
There is a very impressive math whiz hiding inside each of you out there, and it shows up when you really need to solve some life puzzle.
You saved the White House Chief of Security today.

There is also a simpler way to get to these 25 min that define early arrival of the plane.
Look at the picture above.
When security chief received the call that plane landed, he was at the red mark on the road. So, plane was early by as much as it takes for the security chief to get from the red mark to the airport in his bulletproof car. This segment, from the red mark to the plane, is a sum of red-to-purple and purple-to-plane segments. Red-to-purple segment corresponds to 15 min. Now, the purple-to-plane segment...
The bulletproof car never drove it. It turned back at the purple mark taking Mrs Obama from the limousine. If Mrs Obama just waited at the airport and security chief drove all the way to the there, picking Mrs Obama and driving back, they would have arrived to the White House exactly at the expected time. Instead, they were 20 min early. This is because security chief didn't need to drive from the purple mark to the airport and back. So, it takes the security chief 20 min to do this last segment twice. So, it takes 10 min to go from the purple mark to the plane.

Now, add these 10 min to the 15 min from red-to-purple and we see that it takes 25 min for security car to get from the purple mark on the picture above to the plane. This is the early arrival difference.

Anfisa said...

"This is because security chief didn't need to drive from the purple mark to the airport and back" That is it! Anyway, I loved the process itself. Thanks a lot!

Maria said...

Did I mention that you got your first puzzle point? And three new puzzles are coming tomorrow. On this website, in the newsletter, on Facebook and Twitter.