Compound interest and circleSecondary school education teaching for math ( compound interest and circle)
1) same rate interest of 7 year's double of p but how many years this triple interest?
7 years(200-100) =100 tk.
Interest- if its triple interest = (300-100) = 200 tk.
100 tk interest 7 years
1 " " " 7/100
200 " " " 7×100/100 = 14 years.
Answer: 14 years.
2) some tk. 8% interest 3 years provide -interest 1860 tk. After How many year interest 2040?
Example: 8% rate 100 interest of 3 years (8×3) = 24 tk.
Interest - profits 124 tk. So p =100tk.
" 1 " " " 100/124
" 1860 " " 100×1860/124 = 1500 tk.
Interest-p 2040 tk. Interest= (2040-1500) = 540 tk.
Interest-p 1860 tk. Interest (1860-1500) = 360 tk.
Interest 360 tk. Years of 3 .
" 1 " " " 3/360 years.
" 540" " " 3×540/360 years 9/2 years 4 1/2
Answer: 4 1/2
3) 6% interest and profits 1300 tk. Year's of 5. How many years of money 1390 tk.?
Example: 100 tk interest of 1 years 6 tk. 1
100 tk. 5 years interest (6×5) = 30 tk.
100 tk. Years of interest and profits (100+30) = 130 tk.
Ip 130 tk so p100 tk.
" 1 " " " 100/130
" 1300 " " 100×1300/130 = 1000 tk.
1000 tk 5 years interest = (1300-1000) = 300 tk.
Ip 1390 tk interest = (1390-1000) = 390 tk.
1000 tk 300 tk interest 5 years.
1000 " 1 " " 5/300
1000 " 390 " 5×390/300 = 13/2 or 6.5 years.
Answer: 6.5 year
4) Karim shaheb 56000 tk he is some tk annual of interest 12% and due tk 10% he have invested after years total tk 6400 thousand. He Have does get .how much money ?
Example: 12% rate of interest x invested of money10% rate of interest (5600-x) tk.
100 tk 1 years intereste 12 tk.
1 " 1" "12/100
X " 1 " " 12×x/100 = 3x/25 tk.
100 tk 1 years interest 10 tk.
1 " " 1 " " 10/100
(5600-x)" 1 " " (56000-x) x×10/100
(56000-x)/10
Condition apply , 3x/25 + 56000-x/10 = 6400
Or, 6x+280000-5x/50 = 6400
Or, x +280000 = 320000
Ot, x = 320000-280000
So, x 40000 .
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