He will finish at 6:50. It will take him 5 hours and 50 minutes. Hope this helps!
Aye Sir!
8x-24
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Answer: 2mp
Step-by-step explanation: Let "b" represent the speed of the boat in still water
Let "c" represent the speed of the current
Let "t" represent time
Downstream(same direction) =(b+c)*t
Upstream(against current)=(b-c)*t
(b+c)*3=24
(b-c)*4=16
3b+3c=24....all sides can be divided by 3 =b+c=8
4b-4c=16.....all sides can be divided by 4 =b-c=4
Use Elimination method
b+c=8
b-c= 4 Subtracting
=====
2c=4
find c by dividing both sides by 2. c=2
if c=2, substitute to get b
b+2=8
-2=-2
======
b=6
Speed of boat in still water =6mph
rate of current=2mp
Answer:
n = 60.22
Step-by-step explanation:
Hello
To find Sn, we need to draw out equations for each a₇ and a₁₉
In an arithmetic progression,
Sn = a + (n-1)d
Where Sn = sum of the A.P
a = first term
d = common difference
a₇ = 32
32 = a + (7-1)d
32 = a + 6d ........equation (i)
a₁₉ = 140
140 = a + (19-1)d
140 = a + 18d .........equation (ii)
Solve equation (i) and (ii) simultaneously
From equation (i)
32 = a + 6d
Make a the subject of formula
a = 32 - 6d .....equation (iii)
Put equation (iii) into equation (ii)
140 = (32 - 6d) + 18d
140 = 32 - 6d + 18d
Collect like terms
140 - 32 = 12d
12d = 108
d = 108 / 12
d = 9
Put d = 9 in equation (i)
32 = a + 6(9)
32 = a + 54
a = 32 - 54
a = -22
When Sn = 511
Sn = a + (n - 1)d
Substitute and solve for n
511 = -22 + (n-1) × 9
511 = -22 + 9n - 9
511 = -31 + 9n
511 + 31 = 9n
542 = 9n
n = 542 / 9
n = 60.22
