**Explanation :**Let the required cost be Rs. x.

Then, More toys, More cost (Direct Proportion)

15 : 35 : : 234 : x (15 * x) = (35 * 234) x=(35 * 234)/15 = 546

Hence, the cost of 35 toys is Rs. 546.

**Explanation :**. Let the required number of hours be x.

Then, Less men, More hours (Indirect Proportion)

15 : 36 : : 25 : x (15 x x) = (36 x 25) (36 x 25)/15 = 60

Hence, 15 men can do it in 60 hours.

**Explanation :**Let the required wages be Rs. x.

More men, More wages (Direct Proportion)

Less days, Less wages (Direct Proportion)

Men 6: 9 : :2100:x

Days 15:12

Therefore (6 * 15 * x)=(9 * 12 * 2100)

x=\(\frac{(9 * 12 * 2100)}{(6 *15)}\)=2520

Hence the required wages are Rs. 2520.

**Explanation :**Let the required length be x metres

More men, More length built (Direct Proportion)

Less days, Less length built (Direct Proportion)

Men 20: 35

Days 6: 3 : : 56 : x

Therefore (20 x 6 x x)=(35 x 3 x 56)

x=(35 x 3 x 56)/120=49

Hence, the required length is 49 m.

**Explanation :**

**Explanation :**. Let 3 engines of former type consume 1 unit in 1 hour.

Then, 4 engines of latter type consume 1 unit in 1 hour.

**Explanation :**

**Explanation :**The problem becomes:

3300 men taking 850 gms per head have provisions for (32 - 7) or 25 days, How many men taking 825 gms each have provisions for 17 days?

Ration 825 : 850

Days 17: 25 } : : 3300 : x

(825 x 17 x x) = 850 x 25 x 3300 or x = (850 x 25 x 3300)/(825 x 17)=5000

Strength of reinforcement = (5500 - 3300) = 1700.