SAT math problems?

Question

1. 1/2 < y < 3/4 what is a possible value for sq root of y?

2. On a long street the houses are numbered in jumps of 6. That is, the first house has a street number 6, the second 12, and so on. What is the sum of the last digits of the street numbers of the 83rd, 84th, 85th, 86th, and 87th houses?

3. On a street corner there are 3 flashing lights, a red one and a blue one. The red one flashes three times per minute, and the blue one flashes 2 times per minute. If the lights start off flashing at the same time, once ever how many seconds do they flash together?

Thank you for any help on the problems. If you can it's appreciated if you can show the steps and reasoning :].

Answer 1

1.
1/2 < y < 3/4
sqrt(1/2) < y < sqrt(3/4)
sqrt(2)/2 < y < sqrt(3)/2
.707107 < y < .866025

2.
83*6 = 498
84*6 = 504
85*6 = 510
86*6 = 516
87*6 = 522

Answer: 8 + 4 + 0 + 6 + 2 = 20

3. Red one flashes every 20 seconds. Blue one flashes every 30 seconds. They are only together every minute.

Answer 2

1. any value between square root of 1/2 and 3/4 for example one value can be 0.8 note the square root is always positive.

2. last digit for 83rd, 84th, 85th, 86th, and 87th are 8,4,0,6,2 (for example for 83rd the number is 83*6=498 and the last digit will be 8) Sum is 8+4+0+6+2=20

3. Are there two or three flashing lights? for two flashing lights red blue the red flashes each 20 seconds and the blue each 30 seconds. Find the smallest number that can be divided by 20 and 30, i.e., the answer is 60 seconds

Answer 3

1. You must have choices here. The square root can range from about .707 to 0.866.
2. Since the last digits of multiples of 6 repeat after the 5th multiple, the last digit of the 83 to 87th multiple will be 8,4,0,6, and 2. The sum of these digits is 20.
3. Every 60 seconds. The red light flashes at 0, 20 and 40 seconds of each minute. The blue light flashes at 0, 30, and 60 seconds of each minute.

Answer 4

1)
since the question is just asking for a possible value, not all possible values, take any # between 1/2 and 3/4, such as 5/8, and sqrt. 5/8=.65, sqrt of .65=0.790569415

2)

83x6=498
84x6=504
85x6=510
86x6=516
87x6=522
_________
8+4+0+6+2=20

3)

Indeterminate. What is the 3rd light doing?

Answer 5

the first one is sqrt2 / 2 less than or equal to y less than or equal to sqrt 3 / 2, i just took the sqrt of the equation....

on the second one, try using combinations and permutations(type into google)

if the red light flashes 3 times per minute it flashes every 20 seconds while the blue light flashes every 30 seconds, so they will flash together once per minute, or every sixty seconds