Answer to #71:-
Very well done, Janefairfax!

Answer to #67:
Correct, Janefairfax!

#73. If (a + b + c) = 0, then what is a³ + b³ + c³ equal to?

#74. What is the Least Common Multiple of

#74

Do you have a special definition of “least common multiple” for rational numbers?

Otherwise, I find the question meaningless. The rational numbers form a field; therefore every rational number is a multiple of any nonzero rational number whatsoever. Divisibility in the rationals is totally trivial. Moreover, since there is no such thing as a least positive rational, there is no such thing as a “least common multiple” (as I understand it) among rational numbers.

I have never heard of such a thing before.

Nevertheless, as long as you clearly define what you are doing, and your definition makes sense, then everything is fine.

Well, then. “LCM” of the four fractions is

ganesh wrote:

As can be seen, 140/3 divided by 2/3 is 70;
140/3 divided by 4/9 is 105;
140/3 divided by 5/6 is 56;
and 140/3 divided by 7/12 is 80.
All the resultants are whole numbers!

#78. Find the Greatest Common Divisor and the Least Common Multiple of 0.63, 1.05, and 2.10.

#79. Find the greatest number  which on dividing 1657 and 2037 leaves remainders of 6 and 5 respectively.

#80. Find the largest number which divides 62, 132, and 237 to leave the same remainder in each case.

Answers to #75, #77, #79, and #80:
All correct, JaneFairfax!

#82. Eleven persons contributed a certain sum. Nine of them gave $2 each and the other two gave $2 and $2.50 more respectively than the average of all the eleven persons. Find out the sum contributed by the two persons who contributed more.

#83. In a business, A and B received some amount in a certain ratio. B and C received the profits in the same ratio as A and B. If A received $2,500 and C received $3,600, what is the amount received by B?

#84. The ratio of prices of two cars was 16:23.  Two years later, when the price of the first had risen by 10% and that of the second by $477, the ratio of their prices became 11:20. Find the original prices of the two cars.

#85. A person is standing on a railway bridge which is 50 meters long. He finds that a train crosses the bridge in 4½ seconds and crosses him in 2 seconds. Find the length of the train and its speed in kilometers per hour.

#88. A alone can reap a certain field in 15 days and B alone in 12 days. If A begins alone, and after a certain interval, B joins him, the field is reaped in 7½ days. How long did A and B work together?

#89. Three persons A, B and C finished a work. A worked at it for 5 days, B for 7 days and C for 9 days. Their daily wages were in the ratio 4:3:2 and the total earnings amounted to $118.What was the daily wage of each of them?

#90. P, Q, and R can do a piece of work in 6, 8, and 10 days respectively. They begin to work together.  A continues to work till it is finished, B leaves off 1 day before and C leaves off ½ day before the work is finished. In what time is the work finished?

I think it's safe to assume that PQR = ABC.
My guess is supported by the nice answer that follows.