If 100 envelopes cost 70cent how much will 250 cost?

If 100 envelopes cost 70 cents, then the cost per envelope is 0.7 cents (70 cents / 100 envelopes). For 250 envelopes, the cost would be 250 envelopes × 0.7 cents/envelope = 175 cents. Therefore, 250 envelopes will cost $1.75.