Problem Solving

1)The avg and std deviation of a certain normal distribution are 13.5 &1.5 resp.
What vallue is exactly 2 std deviation lessthan the mean?
a)10.5 b)11.0 c)11.5 d)12.0 e)12.5

2) The area of a square garden is "A" sqft & perimtr is P.iF A=2p+9 P=?
A)28 B)36 c)40 d)56 e)64


7)jOHUA AND jOSE WORK AT auto repaie shop along with 4 others.
What is the probablity the J
oshua and jose will be chosen for a programme
a)1/15 b)1/12 c)1/9 d)1/6 e)1/3

Please with me with these questions especially the first one.

golu23 wrote:1)The avg and std deviation of a certain normal distribution are 13.5 &1.5 resp.
What vallue is exactly 2 std deviation lessthan the mean?
a)10.5 b)11.0 c)11.5 d)12.0 e)12.5

Please with me with these questions especially the first one.

Given Average = Mean = 13.5

SD = 1.5 -> 2*S.D = 3

2S.D less than mean = 13.5-3 = 10.5 A IMO

golu23 wrote:
2) The area of a square garden is "A" sqft & perimtr is P.iF A=2p+9 P=?
A)28 B)36 c)40 d)56 e)64

Let the side of the square be 'a' units;

Given area = A = a^2 and Perimeter P = 4a

GIven, a^2 = 2*(4a) + 9

-> a^2 - 8a - 9 =0

a = 9 (or) a = -1 (side cannot be -ve). Hence side = 9

Perimeter = 4*9 = 36 B IMO.

1) As we need to fin d number 2 std deviation less then mean and each SD is equal to 1.5 so answer would be 13.5-3 = 10.5

golu23 wrote:1)The avg and std deviation of a certain normal distribution are 13.5 &1.5 resp.
What vallue is exactly 2 std deviation lessthan the mean?
a)10.5 b)11.0 c)11.5 d)12.0 e)12.5

2) The area of a square garden is "A" sqft & perimtr is P.iF A=2p+9 P=?
A)28 B)36 c)40 d)56 e)64

1. 13.5 - (1.5*2) = 10.5

2. P = 4 * sqrt(2P+9)
P^2 = 16(2P+9)
P^2 = 32P + 144
P^2 - 32P - 144 = 0
(P - 36)(P + 4) = 0
P = 36, -4 (discard -4)
P is 36

3. Sounded like 1/3 * 1/5 = 1/15