Answer:
1. The amount that was not spent is: 1080 soles
2. The answer is 5.
Step-by-step explanation:
Question 1. There are two situations:
If you spent 5/8 of the money then notice, that u did not spend 3/8.
If you spend 2/5 of the money, then you would have 72 more.
So think, this equation:
3/8x + 72 = 2/5x
2/5 of the money is the value for what you did not spend plus 72, the amount you would have, where x is the answer for the total of money.
72 = 2/5x - 3/8x
72 = 1/40x
x = 2880 soles
As you did not spend 3/8 of 2880, the answer is 1080 soles
Notice that if u spent 2/5 of 2880, you would have 1152 soles, so, the 1080 + 72, as the problem said.
Question 2.
We think letters for this excersise.
N = My born year
2020 (this year) - N = E (my age, now)
So N + 10 = when I get 10 years old
N + 20 = when I get 20 years old
N + 30 = when I get 30 years old
N + 40 = when I get 40 years old
The problem says:
(N+10) + (N+20) - (N+E) = 2020
((N+30)+E) - (N-40) = X
So if 2020 - N = E, then notice that 2020 - E = N. Let's replace this in the equation form:
((2020-E)+10) + ((2020-E)+20) - ((2020-E)+E) = 2020
No minus in the first two terms, so we can break the ( )
2020-E+10 + 2020-E+20 - ((2020-E)+E) = 2020
We apply the distributive property for the second term
2020-E+10 + 2020-E+20 - 2020+E-E = 2020
We can cancel two E, and the 2020, so the new form will be:
2020 - 2E + 30 = 2020
We can also cancel the 2020, so if we reorder the equation, we have:
-2E = -30
E = 15 That's my age, so my born's year is 2020 - 15 = 2005 (N)
Look:
(2005 + 10) + (2005+20) - (2005+15) = 2020
So now, the last part
((2005+30)+15) - (2005+40) = 5
