# Q25b 07 hsc (1 Viewer)

#### taker0

##### Member
ok so can anyone explain this one to me? do we use the sine rule to find the angle of elevation? cause i did this:

18/sin15 = 20/sin x .... were x is the angle we gotta find.

it gave me an answer of 16 degrees....but apparently the answer is 56.

what am i doing wrong?? am i looking at the wrong angle?

also my calc is set to deg not rad.

#### PC

##### Member
Your equation is right. But be careful. The answer is 16.71293303, so this is 17° to the nearest degree.

But remember you've found Angle JMK. This is NOT The angle of elevation.

The angle of elevation is angle KML.
Angle KML = 75 – 17 = 58°.

#### taker0

##### Member
thx.

also can some answer the following 06 question? im struggling with probability...

Q28
(a) On a bridge, the toll of 2.50 is paid in coins collected by a machiene. the macheien only accpets \$2, \$1 and 50c coins.

(i) list the combinations used to pay the 2.50

(ii) jill has 3 two dollar coins, 6 one dollar coins and 2 50c coins. she selects 2 at random. wat is the robability the she selects exactly 2.50?

(iii) at the end of the day the macheine contains x two-dollar coins, y one dollar coins and w 50c coins. write an expression for the total value of coins

thanks.

EDIT:

here are my answers...can anyone check them for me??

I:
1,1,50c
50,50,50
2,50

II: 2/10x2/9 = 2/45

III: v=x+y+w

Last edited:

#### PC

##### Member
taker0 said:
Q28 (a)
On a bridge, the toll of 2.50 is paid in coins collected by a machiene. the macheien only accpets \$2, \$1 and 50c coins.

(i) list the combinations used to pay the 2.50

(ii) jill has 3 two dollar coins, 6 one dollar coins and 2 50c coins. she selects 2 at random. wat is the robability the she selects exactly 2.50?

(iii) at the end of the day the macheine contains x two-dollar coins, y one dollar coins and w 50c coins. write an expression for the total value of coins
(i) Try to do it systematically.
No \$2 coins, no \$1 coins, we need 5 x 50¢ coins.
No \$2 coins, 1 x \$1 coin, we need 3 x 50¢ coins.
No \$2 coins, 2 x \$1 coins, we need 1 x 50¢ coins.
1 x \$2 coin, no \$1 coins, we need 1 x 50¢ coins.
That's it. Any more and we'll be over. So 4 different combinations of coins.

(ii) To select two coins at random and get exactly \$2.50, she'll need to pick a \$2 coin and a 50¢ coin. All the other combinations need more than 2 coins.

So Probablity = P(\$2 then 50¢) or P(50¢ then \$2)
= 3/11 x 2/10 + 2/11 x 3/10
= 6/55

(iii) Total value = (x x \$2) + (y x \$1) + (w x 50¢)
= 2x + y + 0.5w

#### savio23q

##### Band
taker0 said:
thx.

also can some answer the following 06 question? im struggling with probability...

Q28
(a) On a bridge, the toll of 2.50 is paid in coins collected by a machiene. the macheien only accpets \$2, \$1 and 50c coins.

(i) list the combinations used to pay the 2.50

(ii) jill has 3 two dollar coins, 6 one dollar coins and 2 50c coins. she selects 2 at random. wat is the robability the she selects exactly 2.50?

(iii) at the end of the day the macheine contains x two-dollar coins, y one dollar coins and w 50c coins. write an expression for the total value of coins

thanks.

EDIT:

here are my answers...can anyone check them for me??

I:
1,1,50c
50,50,50
2,50

II: 2/10x2/9 = 2/45

III: v=x+y+w

#### taker0

##### Member
thnaks for the replies really helped me out, sorry i accidently posted it twice.

savio23q said: