waytouing

For 1, 1.5 std dev is 0.3*1.5 around the mean 8.1

2. rate 1= x, rate two= 1.5x, then get x from the 4 hrs given, then use 1/(1.5x), get ans

3.in 1 sec, rev= x/60, so k secs, (kx)/60

4.(16s)/n