Sue has $2.80 in dimes and nickels. If she has 13 more dimes than nickels, how many of each coins does she have?

1 answer:

5 0

I have seen this question before and I think you meant 10 more dimes than nickels.

We can use substitution to answer this question. The value of a nickel is 5 cents, and we can use the variable n to represent the number of nickels. The value of a dime is 10 cents, and we can use the variable d to represent the number of dimes.

First lets figure out the equations.
.10d+.5n=2.80 (the number of nickels (n) multiplied by .5 will tell us their money value. Same thing for the dimes)
d-n=10 (since there are 13 more dimes than nickels, the number of dimes value (d) minus the number of nickels value (n) will give us 10)

Now lets isolate a variable in one of the equations, preferably the second one because it doesn't have any visible coefficients,

d-n=10
-n=10-d (subtracted the d from both sides)
n=-10+d (made the n positive)

Now that we have the value of n, we can plug it into the other equation.

.10d+.05n=2.80
.10d+.05(-10+d)=2.80 (we replaced the n with the value that we previously got)
.10d-.5+.05d=2.80 (did the multiplication)
.15d-.5=2.80 (combined like terms)
.15d=3.30 (added the .5 to both sides)
d=22 (divided both sides by the .15)

Now that we know that there are 22 dimes and we also know that there are 10 less nickels than dimes, so we can subtract 10 from 22 to get the number of nickels. 22-10=12

d=22
n=12

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6. Fill in the smallest digit to make the number divisible by:

Degger [83]

Answer:

(i) 71640, 321970

(ii) 1143, 47205, 2316

(iii) 1428, 9252, 7212

(iv) 24620, 9100, 6700

(v) 12320, 59016, 46424

Step-by-step explanation:

(i) In order for any number to be divisible by 5, its last digit must be either 0 or 5.

In this case, we should add a last digit, so we opt for 0 without any doubt since it gives a smaller number than 5 as the last digit: 71640 is smaller than 71645, the same way as 321970 is smaller than our second option, 321975.

(ii) If the sum of a number's digits gives a number divisible by 3, then the main number is also divisible by 3.

This means that we have to do some addition:

1_43: 1 + 4 + 3 = 8. Eight is not divisible by 3. But 9 is. So the smallest digit we can add for it to be divisible by three is 1: 1143.

47_05: 4 + 7 + 0 + 5 = 16. Since 16 is not, the next number that is divisible by 3 is 18, and therefore, the smallest digit we need here is 2: 47205.

_316: 3 + 1 + 6 = 10. Twelve is the next number divisible by 3, and that means 2 is the digit we choose: 2316.

(iii) Only numbers that are divisible by both 2 and 3 are also divisible by 6.

_428: In order for a number to be divisible by 2, its last digit must be 0 or divisible by 2. That is already the case here.

4 + 2 + 8 = 14 which is not divisible by 3. But 15 is. So the smallest digit we need is 1: 1428.

9_52: The number will be divisible by 2. And 9 + 5 + 2 = 16 which is not divisible by 3 but 18 is. This means the smallest digit we need is 2: 9252.

721_: Since the last digit can be any of these 0, 2, 4, 6, 8 for the number to be divisible by two, we will first see what digit we need for it to be divisible by 3.

7 + 2 + 1 = 10 which is not divisible by 3 but 12 is. We will then choose to add 2: 7212.

(iv) A number is divisible by 4 only if the number that is formed by its two last digits is also divisible by 4..

2462_: Since we need to add a last digit, this should be easy. The smallest two-digit-number that starts with 2 and is divisible by four is 20: 24620.

91__: Here we need to add both of the two last digits, and this should be the easiest example! All numbers that end in 00, meaning they have a round number of hundreds, are divisible by 4! Therefore our option is: 9100.

670_: In this case, we apply the same rule from the last example - and we choose 0: 6700.

(v) In order for a number to be divisible by 8, its last three digits need to be divisible by 8, or it can end in 000, since every number having a round number of thousands is also divisible by 8.

1232_: 320 is divisible by 8 since 8 × 40 gives 320. Therefore, our smallest digit here is 0: 12320.

59_16: If we add a 0 here, the last three digits form the number 016, which is divisible by 8. Our choice is again zero: 59016.

4642_: Unfortunately, 420 is not divisible by 8. The next number closest to 420 and which is divisible by 8 is 424. Its division by 8 gives 53. Therefore we should add 4: 46424.

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3 years ago

Does anyone knows question 35

amid [387]

Answer: -3≤x ≤3
I can do more if needed