एक वृत्त की त्रिज्या को इस प्रकार बढ़ाया जाता है कि उसकी परिधि में 7% की वृद्धि होती है। परिणामस्वरूप, वृत्त के क्षेत्रफल में कितने प्रतिशत की वृद्धि होगी?

A person saves 90% of his income. If his expenditure is ₹520, find his income (in ₹).

By how much is 30% of 60 greater than 25% of 40?

By how much is 30% of 50 greater than 35% of 30?