Answer:
-51.4
Step-by-step explanation:
X - number of 5 c stamps,
y - number of 15 c stamps,
z - number of 25 c stamps.
The system:
x + y + z = 160
y = 3 x
0.05 x + 0.15 y + 0.25 z = 25 / * 100
-------------------------------------------------
x + y + z = 160
y = 3 x
5 x + 15 y + 25 z = 2500 / : 5
----------------------------------------
x + 3 x + z = 160
x + 3 y + 5 z = 500
-------------------------
4 x + z = 160 / * ( - 1 )
10 x + 5 z = 500 / : 5
------------------------------
- 4 x - z = - 160
+
2 x + z = 100
-------------------------
- 2 x = - 160
x = 30, y = 90
z = 160 - 120 = 40
Answer:
- 30 of 5 c stamps,
- 90 of 15 c stamps,
- 40 of 25 c stamps.
Answer:
314.16
Step-by-step explanation:
area = pi x r2. 3.14 x 100 = 314.16
Answer:
7 metre
Step-by-step explanation:
Let the breadth of the room is x.m. , then the length is (x+2).m. , accordingly:-
(x+2).x. = 63.
or, x^2 +2 x - 63 = 0.
or, (x + 9).(x -7) =0.
or, x = - 9 (not valid) , 7 .
Thus , the length = (x+2).m.= (7+2) = 9.m. , breadth = x .m. = 7.m. , Answer.
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