If we interpret the meaning of: “After ten years”.. 10 years from now then the answer is M=50 AND D=20, here  10 years ago M=50-10 =40 and D-10=10 is ===> (M=D*4),  and 10 years from now M=50+10 =60, D+10=20+10 =30 so M*2D.
But if it means after the first situation which brings it to present time then the answer will be M=30 D=15 (M-10 = 30-10 = 20 = (D-10 = 15-10 =5) *4, & M=30 = 2*D(=15)

start the 2 clocks.
After 4 minutes, flip the 4-minute clock over.
after 7 minutes flip the 7 minute clock.
After 8 minutes, the sand ended on the 4 minute clock for the second time,
which means that a minute passed on the 7 minute clock. Flip back and we got 9 minutes.

The hands will overlap every 360/5.5 minutes =(65.4545… = 1hr 5min +27.27 sec) so on 1:05, 2:10, 3:16,  4:21, 5:27, 6:32, 7:38,  8:43, 9:49,  10:54

She was part of a relay race competition and during the race she made a world record   on the part she run. So the as part of a group she got a silver medal and for her own achievement she got a gold medal

All mangoes were on the leaves that are on the ground

Time (minutes) = Distance *60 / speed (mph) so 60*10/50 =12 min.
So we have (20-12=8) minutes for return
so according to above  formula 60*10/8 =75 (mph)

There are not enough details to answer the question. The ball has a of course some weight. If converting 9o feet to millimeters  its 27432. If the ball weight is such that it can’t bunce less than 1mm and since 2^15=32768 so the answer will be up to 14 times at most

According to the 1st fact that: Mr. Blue said: “…we are all wearing different colored shirts from our names” we have two options

1) Mr. Blue : red shirt
Mr. Red : white shirt
Mr. White : blue shirt

2) Mr. Blue: white shirt
Mr. red: blue shirt
Mr. white: Red shirt
but since the man wearing the white shirt said:  ‘Wow, Mr. Blue, that’s right!’  it can’t be option 2 (he is wearing the white shirt) So option 1 is the right answer.

Or the bottle is without bottom.