F.2 Math急急!!!!!!!

1. An insect flies at a speed of 9.0m/s, correct to the nearest 0.5m/s.
(a) The upper limit of its actual speed is 9.0+0.5 = 9.5 m/s.
(b)The lower limit of its actual speed is 9.0-0.5 = 8.5 m/s.

2.It is given that a:b:c=3:5:4 . If b=6,then
a= b x 3/5 = 6(3/5) = 3.6 and c= b(4/5) = 6(4/5) = 4.8.

3.It is given the formula 1/u=1/f-1/v. If f=5 and u=15 ,
1/15 = 1/5 - 1/v
v = 1/(1/5 - 1/15)
then v= 7.5.

4.Given that the n^th term of a sequence is 3^n-2,
the 6^th term of the sequence is 3^(6-2) = 3^4 = 81

5.Betty deposits $15000 in a bank for 3 years . The bank pays simple interest at a certain interest rate per annum. If Betty gets an amount of $18150 at the end of the period , what is the interest rate per annum?(show your working )

R = interest rate , I (principle + interest) = 18150 - P = 3150,
P(principle) = 15000, T = 3 years

I = P(R)(T)
3150 = 15000(R)(3)
R = 0.07 = 7%

I don't know sorry.
Ask your parent or teacher or a person who is older than u