Answer:
At 7% $54,000
At 9% $156,000
Step-by-step explanation:
Let x be the amount invested at 7%, Then 2x + 48000 will be the amount invested at 9%
We know that:
7% = 0.07 & 9% = 0.09
So we can write the interest equation as follows:
0.07x + 0.09 (2x + 48000) = 17820
0.07x + 0.18x + 4320 = 17820
0.25x + 4320 = 17820
Subtracting 4320 from both sides of the equation we get:
0.25x = 17820 - 4320
0.25x = 13500
Dividing both sides of the equation by 0.25 we get:
x = 13500 / 0.25
x = $54,000 invested at 7%
&
2 x 54000 + 48000
= $156,000 invested at 9%
Hence the amount invested at 7% is $54,000.
& the amount invested at 9% is $156,000.
Answer:
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Answer:
a) 820
b)450
c) -540
d) -294
e) 1440
f) 1425
Step-by-step explanation:
a) it is an arithmetic progression with ratio=4
a1=3,
a2=3+r=3+4=7.....
a20=a1+19r
so a20=3+19*4=3+76=79
S=(a1+an)*n/2 where n=20
so S=(3+79)*20/2=820
b) a15=a1+14*r=2+14*4=2+56=58
S=(a1+a15)*15/2=(2+58)*15/2=60*15/2=30*15=450
It is the same formula for all the exercises
S=(a1+an)*n/2 , where n is the number of terms
c) a40=30+39*(-3)=30-87=-57
So S=(30-57)*40/2=-540
d) a14=5+13*(-4)=5-52=-47
S=(5-47)*14/2=-42*14/2=-42*7=-294
e) it is 5+7+9+......+75
nr of terms = (an-a1) :r+1=(75-5):2+1=36
S=(5+75)*36/2=36*40=1440
f) ratio=7-4=3
the same formula for n= (91-4):3+1=87:3+1=29+1=30
S=(4+91)*30/2=95*30/2=2850/2=1425
